source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
OpenBookQA | OpenBookQA-501 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Viruses are killed by objects used in a | [
"backyard",
"bathroom",
"kitchen",
"living room"
] | C | adding heat to something kills viruses in that something |
OpenBookQA | OpenBookQA-502 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
An example of weathering is | [
"sand",
"sharp boulders",
"tall trees",
"coral reefs"
] | A | sometimes weathering rounds rocks |
OpenBookQA | OpenBookQA-503 | orbit, the-sun, earth
Notes:
It takes the Earth 365.256363004 days to revolve around
the Sun with respect to the fixed stars, but the time
between vernal equinoxes is slightly less (365.242190402
days) because the position of the vernal equinox moves
(precesses) with respect to the stars. Source:
http://hpiers.obspm.fr/eop-pc/models/constants.html
The Gregorian calendar's average day length of 365.2425
is much closer to 365.242190402 days than the Julian
calendar's 365.25 average day length, but it's still not
perfect. As noted in
Do solstices and equinoxes shift over time?
if we continue using the Gregorian calendar in the far
future, the equinoxes and solstices will drift
backwards. By 17090 (the limit of DE431), they will look
like this:
EQU 476198945887.238159 A.D. 17090-02-22 08:56:59
SOL 476207018540.040894 A.D. 17090-05-26 19:21:11
EQU 476214808218.146362 A.D. 17090-08-24 23:09:09
SOL 476222655067.609985 A.D. 17090-11-23 18:49:59
about a month behind their "regular" times.
MY EARLIER PARTIAL ANSWER FOR REFERENCE:
Since HORIZONS (http://ssd.jpl.nasa.gov/?horizons) and SPICE (http://naif.jpl.nasa.gov/naif/tutorials.html) can compute the ecliptic and solar position back that far, it should be possible to compute equinoxes and solstices with reasonable accuracy. However, I haven't been able to find a site that actually lists these dates (I'm pretty sure USNO did this at one point, but I can't find their list). Other possibly helpful sources/questions:
The following is multiple choice question (with options) to answer.
How long does it take Earth to fully revolve one time | [
"28 hours",
"46 hours",
"1400 minutes",
"1440 minutes"
] | D | a Rotation of the Earth on itself takes one day |
OpenBookQA | OpenBookQA-504 | biochemistry, metabolism, bioenergetics
Title: What is the energy source for adipocytes? Since adipocytes export fatty acids and glycerol and don't use them as an energy source, what is the main source of energy for adipocytes? Adipocytes use glucose as an energy source. They express the insulin-responsive glucose transporter GLUT4 just like muscle cells so that when blood glucose levels rise they are primed to take the glucose up for fatty acid biosynthesis, but they also use glucose as a fuel molecule.
The following is multiple choice question (with options) to answer.
What is a source of energy for animals? | [
"rocks",
"plastic food",
"metal",
"nutriment"
] | D | food is a source of energy for animals |
OpenBookQA | OpenBookQA-505 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
If a deer is unable to eat regularly, or only eats that which lacks essential minerals, the deer may | [
"find healthy food",
"experience failing health",
"fail to gestate",
"prepare to mate"
] | B | an animal requires enough nutrients to maintain good health |
OpenBookQA | OpenBookQA-506 | a) Draw a Free Body Diagram including the particle, the inclined plane and all forces acting on the particle with their labels. Determine the position onthe meter stick at which one would hang a third mass of 0. Then show the three forces extending from that point that are from the hanging mass, the string tension and the tension in the meter stick. They may be copied and cited in published work if the University of Maryland Fermi Problems site is mentioned and the URL given. A 20-gram cube is hanging 10 centimeters from the right end. Hang a 200 gram mass at the 10 cm mark, hang the spring scale at the 90 cm mark, suspend the meter stick from the 50 cm mark. How do I find the. The spring constant in the above graph is 20 Newtons per meter, or 20 N/m. Use the 500-g spring balance to determine the mass of your "weights. Where (at what mark) should a third mass of 0. If you have an old-style prepayment meter, you can ask your energy supplier to replace it with: an old-style credit meter - this type of meter doesn't let you prepay for your energy a smart meter - this type of meter has a prepayment setting your supplier can turn on or off Your supplier usually won. (a) By how much does the. The store is extra-proud of the flag because it's an extra-big one (to check it out, see the figure). 6) or, upon. Each equation contains four variables. It is a simple device that measures force by measuring the amount that the force stretches a spring. 1 $\mathrm{m}$ from its end. How much force must be hanging from the 70. Then, students hang 2 different masses on each side of the balancing point, record their locations, and calculate the torque on the stick. 1 The Nature of Physics Physics is the most fundamental and all-inclusive of the sciences, and has had a profound effect on all scientific development. A seesaw is a type of lever. I will hang the spring. Make a torque-balance sketch similar to the one in. (25 points) A pair of fuzzy dice is hanging by a string from your rearview window. Every time the meter stick swings back and forth the axle squeaks. Activity-Based Physics GLOBE Program This set of parts constructs a complete Meter Stick Torque lab. It is a simple device that measures
The following is multiple choice question (with options) to answer.
What United States unit of measurement would be most comparable to a meter stick | [
"Mile Marker",
"ruler",
"Tape Measurer",
"Yardstick"
] | D | a meter stick is used to measure length |
OpenBookQA | OpenBookQA-507 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
Coyotes notice that their territory begins to get more and more dry. This means that in order to properly hydrate, the coyotes will need to | [
"mitigate water",
"moisturize their fur",
"migrate for dryness",
"migrate for fluid"
] | D | as dryness increases in an environment , the available water in that environment will decrease |
OpenBookQA | OpenBookQA-508 | visible-light
Title: How does a flashlight work? How would that be effected in the vacuum of space or on another planet? I was wondering if it was possible to explore the dark side of the moon. I've been trying to figure out a light source so things there can be seen. What we call the "dark side" of the moon is just the side that is not visible from Earth. That side is illuminated by the sun just as often as the side that we can see. But when it is in the light, we don't see it.
As for your other question: conventional flashlights work by sending a current through a light source (incandescent bulb, or these days increasingly LEDs). Either of these will work fine in vacuum.
The following is multiple choice question (with options) to answer.
Flashlights | [
"illuminate a person's age",
"need remote controls to properly operate",
"make it easier to spot cat toys under the couch",
"make word searches easier"
] | C | a flashlight emits light |
OpenBookQA | OpenBookQA-509 | newtonian-mechanics, everyday-life, collision
Title: Physical Role of Batter in Baseball Physically, what is the role of a batter in baseball?
My question is inspired by How does the speed of an incoming pitch affect the speed of a baseball after it's hit?
The answer to that question, that a faster pitch results in a farther hit, surprised me. I had thought that a batter was solely applying impulse to the ball (mass * velocity of bat = Force * time on ball). Clearly the batter is doing more.
Specifically, I'm interested in what information we'd need to know and what math we'd use to calculate the final velocity of the ball. It helps to think of the extreme cases here. If the bat was not moving (like a bunt), the resulting bounce does depend on incoming speed. Now, make the incoming ball really slow and the batter hitting fast. The result does not depend on incoming speed. The true answer is the superposition of these two cases.
The following is multiple choice question (with options) to answer.
When a baseball is hit with a bat the ball particles do what? | [
"Fly",
"Vibrate",
"Talk",
"Roll"
] | B | hitting an object causes the particles in that object to vibrate |
OpenBookQA | OpenBookQA-510 | meteorology, snow, radar
Also note that winter precipitation adds an extra complication because the particles are lighter in weight and can thus be blown about more by vertical and horizontal winds. Raindrops (and hail) are quite likely to fall unless extreme updrafts exist because they are heavy. But drizzle, snow, and sleet may be blown around quite a bit. Without a time-intensive dual-Doppler analysis, you cannot know the wind motion in the storm thoroughly, and therefore will have varying results at times.
And finally, the big wrench is unfortunate inherent to how radars work. They measure the percentage of their sent energy that is reflected back to them. That's great because that's directly connected to the diameter of the item falling (to the 6th power). But unfortunately the grand problem is that in a storm, there is a huge variety of drop/flake sizes mixed together at once... such that we can't extract which combination of particle sizes created it (and thus can't calculate volume to actually know the rain/snow amount that falls). It could be like 6 medium size flakes causing the 10 dBZ echo... or 2 large flakes and 10 small flakes... and each combination is a different volume/snow total. (to see the nitty-gritty math details on this, read more here.) So we can never know for sure the exact rain/snow falling using just radar. The good news is we've at least done lots of experiments and come up with some fairly useful best-practice formulas for using the Z-R ratio in different scenarios. Good, but not perfect.
The following is multiple choice question (with options) to answer.
When it is sleeting outdoors, that is because precipitation | [
"melted",
"evaporated",
"solidified",
"rained"
] | C | sleet is made of ice |
OpenBookQA | OpenBookQA-511 | Paul T. provides a good answer regarding the case where the height of the bottoms of the poles are the same (which is what was asked for in the question). The main difference in that case is due to the different heights of the centers of mass of the two rods.
However, you might ask, what if the centers of mass of the two rods were at the same height, would there still be a difference? It turns out that there will be, although the difference is even smaller.
Let $$m$$ and $$l$$ be the mass and length of a vertical rod of uniform density, and $$r$$ the height of its center from the center of the planet. The planet's mass is $$M$$. Consider a tiny piece of the rod, of mass $$\delta m$$ and distance $$x$$ from the rod's center (so $$x$$ is between $$-l/2$$ and $$+l/2$$). The force of gravity on the tiny piece is:
$$\delta F=\frac{GM\delta m}{(r+x)^2}$$
The total force on the rod is the integral of $$\delta F$$ over the whole mass:
$$F=\int\frac{GM}{(r+x)^2}dm$$
The mass of the small piece is proportional to its length ($$m/l=\delta m/\delta x$$) so we can substitute $$dx$$ for $$dm$$ with the appropriate scaling:
$$F=\int_{-l/2}^{+l/2}\frac{GM}{(r+x)^2}\left(\frac{m}{l}dx\right)$$
Doing the integral yields:
The following is multiple choice question (with options) to answer.
I left a statue outside away from water for 100 years, when I come back it is significantly smaller, why? | [
"The Wind",
"Birds",
"Tiny Trolls",
"Ants"
] | A | wind causes erosion |
OpenBookQA | OpenBookQA-512 | physical-chemistry, reaction-mechanism, enthalpy, free-energy
I would think that in order to be able to go to the intermediate state, one needs to provide energy, thus that it could not be spontaneous for this reason. One needs to provide energy, for example by heating, that is increasing temperature.
How is that possible? Any comment? "Spontaneous" means different things in different contexts
Your penultimate paragraph captures a key idea. The explanation for why this is right requires a recognition of the context of the term "spontaneous".
The context of the statement at the start of the question $\Delta G=\Delta H-T\Delta S$ is negative is thermodynamic stability. But this is somewhat at variance with the more natural use of the term which implies "things happen without being pushed". This idea is closer to the idea of kinetic stability in chemistry.
You correctly identify the need to add energy to get the reaction past the transition state. Even if the reaction overall releases energy (thermodynamically spontaneous) the reaction won't just happen if there is a huge barrier to getting over the transition state. There are big kinetic barriers that stop the reaction "just happening". Oxygen and gasoline will react to release energy but this doesn't happen without the push given by the spark plug in the engine of a car.
That barrier is so low in some cases a compound will react with nearly everything with little excuse (chlorine trifluoride will set fire to asbestos). That is a spontaneous reaction in any context. Luckily, few thermodynamically spontaneous reactions are also kinetically spontaneous or humans would catch fire in air.
So when you see the term "spontaneous" ask what is the context: thermodynamic or kinetic? And don't confuse them.
The following is multiple choice question (with options) to answer.
Gasoline is unable to exist without the addition of raw materials such as | [
"fossilized matter",
"sand",
"water",
"air"
] | A | oil is a source of gasoline |
OpenBookQA | OpenBookQA-513 | ocean, ocean-currents, tides
Direct disruption of seabed habitats by physical interference, e.g. from moorings
Disruption of ecological niches: Some organisms have evolved to survive in areas where others cannot - e.g. high current speed environments. Changes in seabed conditions, e.g. from greater or lesser current speeds, may cause them to be out-competed by other species that can then settle there.
Similarly, changes to sediment distribution represent changes to seabed habitats.
Alteration of flow patterns could have implications for species with a dispersive juvenile stage (e.g. larvae that rely on currents to spread) or those that rely on current flow for nutrient or waste transport.
The following is multiple choice question (with options) to answer.
A destroyed habitat can lead to | [
"raccoons losing their homes",
"birds migrating to the north",
"a boom in animal reproduction",
"hibernation of local bears"
] | A | if a habitat is destroyed then that habitat can not support animals |
OpenBookQA | OpenBookQA-514 | recursion, unit-testing, interview-questions, perl
return 0;
}
# returns a list of all Sinks in the matrix
# O(N * M) where N = # of rows and M = # of cols
sub find_sinks {
my ($self) = @_;
my @sinks;
for my $row ( 0 .. $self->rows - 1 ) {
for my $cell ( @{ $self->field->[$row] } ) {
push @sinks, $cell
if $self->is_sink($cell);
}
}
return @sinks;
}
# given an Array of Sinks, find the Basins in this field
# O(n)
sub find_basins_from_sinks {
my ($self, @sinks) = @_;
my %basin;
my $basin_marker = 'A';
# determine how many cells eventually flow into this one
for my $sink ( @sinks ) {
$basin{$basin_marker++} = $self->basin_size($sink);
}
return %basin;
}
# recursively find the number of Cells in the Basin
# attached to the given Cell
sub basin_size {
my ($self, $cell) = @_;
my $size = 1;
for my $neighbor ( $cell->get_flowing_neighbors($self) ) {
$size += $self->basin_size($neighbor);
}
return $size;
}
1;
} # end Rainfall
Unit tests that verify results to match the example cases above:
{ # Tests
use Test::More tests => 4;
{ # 3x3 field
my $r = Rainfall->new( rows => 3,
cols => 3,
field => [ [1, 5, 2],
[2, 4, 7],
[3, 6, 9] ]);
my @sinks = $r->find_sinks;
my %basin = $r->find_basins_from_sinks(@sinks);
is_deeply(
[sort { $b <=> $a } values %basin],
[7, 2],
'Correctly divided 3x3 field into 2 basins'
);
}
{ # 1x1 field
my $r = Rainfall->new( rows => 1,
cols => 1,
field => [ [1] ]);
The following is multiple choice question (with options) to answer.
What is an example of runoff? | [
"A farm being irrigated",
"Water running from a farm into Lake Huron",
"Rainwater soaking into the ground",
"Water condensing to form dew"
] | B | runoff is when cropland water enters bodies of water |
OpenBookQA | OpenBookQA-515 | ecology
Title: Statement about Tropical Rainforests I made a statement about tropical rainforests, and I want to know if it's somewhat true or not:
The soil in tropical rainforests is not exceptionally fertile, because it contains few minerals. The reason that a tropical rainforest has a huge amount of vegetation is because of the quick mineralisation. If a dead leaf falls onto the ground, it immediately gets turned into minerals, which the plants immediately use for sustaining theirselves There are many websites which describe this phenomenon. They all seem to confirm the basic premise of the question: in tropical rain forests most of the minerals are held in the biomass and rapid decomposition contributes to the recycling of these nutrients for new growth. One example is here.
Tropical rainforests are noted for the rapid nutrient cycling that occurs on the ground. In the tropics, leaves fall and decompose rapidly. The roots of the trees are on the surface of the soil, and form a thick mat which absorbs the nutrients before they reach the soil (or before the rain can carry them away). The presence of roots on the surface is a common phenomenon in all mature forests; trees that come along later in succession win out in competition for nutrients by placing their roots over top of the competitors, and this pattern is seen in the temperate rainforest as well. What does not occur in the temperate rainforest, however, is a rapid cycling of nutrients. Because of the cold conditions and the acidity released by decomposing coniferous needles on the forest floor, decomposition is much slower. More of the nutrients are found in the soil here than would be the case in a tropical forest, although like the tropical forest most of the nutrients are held in the plants and animals themselves.
I looked for actual evidence of these differences in rates of decomposition and I found this:
Salinas, N. et al. (2011) The sensitivity of tropical leaf litter decomposition to temperature: results from a large-scale leaf translocation experiment along an elevation gradient in Peruvian forests. New Phytologist 189: 967-977
The following is multiple choice question (with options) to answer.
Peat is made by decaying vegetation compacted by soil in a | [
"uncultivated swamp or marsh",
"river that flows with freshwater",
"geographically separated saltwater ocean",
"lake surrounded by land with a basin"
] | A | peat is made of decaying vegetation compacted by soil in a swamp over a long period of time |
OpenBookQA | OpenBookQA-516 | everyday-chemistry, cleaning, minerals
Once you've got the crystal to the cleanliness you're happy with, you can polish it with powdered polish and a cloth, given time.
If instead of nice, angular crystals you're just trying to produce something like a smooth, rounded stone, after cleaning with water you can use a series of sandpapers (start at 60-80 grit and work up to ~400 grit) and polish to gradually smooth, then polish the stone by hand. This will clear away any deposits, but it will also change the surface of the stone itself. That might be acceptable to you if you've got something like a quartz river rock, and it will make a very nice end product. Take care to keep the stone wet while working, you don't want to breathe in rock dust if you don't have to.
The following is multiple choice question (with options) to answer.
A miner is searching for stones and rocks that can be used for other purposes than for building. He wants to be able to find and process something worthwhile, so he looks for rocks with | [
"aluminium",
"sand",
"roxys",
"pearl"
] | A | rocks sometimes contain aluminum |
OpenBookQA | OpenBookQA-517 | meteorology, barometric-pressure, radiosounding
But you'll find that pressure at the ground is lower in most locations than is indicated on such a map. This is because, despite being called "surface maps", they're actually sea-level pressure maps. At any station situated above sea-level a weather balloon cannot acquire that sea-level pressure. So the pressure must be extrapolated downward using these same equations.
But that still doesn't answer why we'd opt for isohypses...
One benefit may be that height maps are similar to topographic maps.
But it well truly stem from early meteorological rules of thumb. One important forecasting tool before advanced weather models came from the thickness equation (an application of the hydrostatic approximation). It works out that the thickness between 500 mb and 1000 mb was a helpful indication of what kind of precipitation would fall. Values lower than 5400 m indicate that the air column is probably cold enough for snow.
It seems quite feasible that this was relationship was noticed even before the equations were understood. 1000 mb is very close to the surface pressure in many of the big cities during the early development of meteorology (such as New York City, Boston, London, and Paris). So all they'd need to notice is a connection of the 500 mb height and the precipitation type. This might be easier than spotting a pattern of ratios of 5400 m pressure values to surface pressure values around 0.5.
In the end, it probably goes back to how early upper-air observations were recorded. It may well have been some guy going up in the balloons until radio, so would they have recorded at equal heights or equal pressures? Or when radio and the early instrumentation were developed, what would draw them to choose set pressures or set heights? I don't know the history well enough to give a certain answer to that.
In the modern era, models quite often use pressure coordinates (or similar sigma coordinates). In addition, if you wished to calculate the quasigeostrophic omega equation or apply the quasigeostrophic height tendency equation, perhaps equal pressure maps might be slightly more useful. However, I tend to doubt either of these are nearly significant in the overall development of the practice.
The following is multiple choice question (with options) to answer.
A higher barometer reading means | [
"lower air pressure in the atmosphere",
"an atmosphere lacking in air pressure",
"greater air pressure in the atmosphere",
"that the barometer is broken"
] | C | as air pressure increases , the reading on a barometer will rise |
OpenBookQA | OpenBookQA-518 | telescope, mars
Have a look at this guide explaining how consumer-grade computer webcams can be used. It contains a neat comparison of a single frame and a stacked image.
Please note that I'm merely speculating as to which techiniques could be used to obtain such images. I can see that the author posted their email on the S&T site and that there's a comments section as well. Feel free to ask them yourself.
The following is multiple choice question (with options) to answer.
A camera can take an image and | [
"preserve it",
"edit it",
"lock it in",
"produce it"
] | A | a camera is used for recording images |
OpenBookQA | OpenBookQA-519 | everyday-life
Due to friction effects though, option c is still best. Pedaling hard will quickly deplete energy reserves while pedaling at a slow but steady rate will allow you to cycle for much longer. From a physics point of view, we cannot help you spend less energy, it will inevitable take about the same amount of energy regardless of your method (some +/- due to friction, etc). But by keeping your power usage low, you can go much farther before needing a rest. It is much the same as with running and walking. Simplistic physics says both use the same amount of energy, but you won't get as far by running due to the massive power requirements.
The following is multiple choice question (with options) to answer.
Spending less time in the shower | [
"depletes a vast amount of water reserves",
"is bad for the environment",
"uses up more water",
"leads to more reserves in the water heater"
] | D | as time spent taking a shower decreases , water used will decrease |
OpenBookQA | OpenBookQA-520 | Kudos [?]: 132821 [4], given: 12378
Re: A small, rectangular park has a perimeter of 560 feet and a diagonal m [#permalink] 13 Nov 2014, 13:09
Display posts from previous: Sort by
The following is multiple choice question (with options) to answer.
National parks have rules | [
"that curtail the growth of fragile animal species",
"that open the parks to mining of natural resources",
"that allow for littering",
"that protect vulnerable animal inhabitants int he parks"
] | D | national parks limit hunting |
OpenBookQA | OpenBookQA-521 | $\{a_4\}$
$\{a_4,a_1\}$
$\{a_4,a_2\}$
$\{a_4,a_2,a_1\}$
$\{a_4,a_3\}$
$\{a_4,a_3,a_1\}$
$\{a_4,a_3,a_2\}$
$\{a_4,a_3,a_2,a_1\}$
$\{a_5\}$
$\{a_5,a_1\}$
$\{a_5,a_2\}$
$\{a_5,a_2,a_1\}$
$\{a_5,a_3\}$
$\{a_5,a_3,a_1\}$
$\{a_5,a_3,a_2\}$
$\{a_5,a_3,a_2,a_1\}$
$\{a_5,a_4\}$
$\{a_5,a_4,a_1\}$
$\{a_5,a_4,a_2\}$
$\{a_5,a_4,a_2,a_1\}$
$\{a_5,a_4,a_3\}$
$\{a_5,a_4,a_3,a_1\}$
$\{a_5,a_4,a_3,a_2\}$
$\{a_5,a_4,a_3,a_2,a_1\}$
$\{a_6\}$ $\{a_6,a_1\}$
$\{a_6,a_2\}$ $\{a_6,a_2,a_1\}$
The following is multiple choice question (with options) to answer.
A | [
"bacterial cell must perform all life functions",
"lung cell",
"flower cell",
"tail cell"
] | A | if a cell can not specialize then that cell must perform all life functions |
OpenBookQA | OpenBookQA-522 | meteorology, atmosphere, wind, air-currents
Title: Where does wind come from? Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air? Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind.
There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a role. The equation of motion is the Navier-Stokes and in vector form in Cartesian space is:
$$\dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \times \mathbf u + \mathbf g + \mathbf F$$
In this equation, $\mathbf u$ is the vector wind, $(\mathbf u \cdot \nabla)$ is the advection operator, $\rho$ is density, $\mathbf \Omega$ is the vector rotation of the Earth, $\mathbf g$ is effective gravity and $\mathbf F$ is friction.
The LHS is the time rate of change of the wind at a point in space (as opposed to following the parcel). The RHS represent a number of factors that produce a change in the wind. From left to right:
Advection of momentum (non-linear)
Pressure gradient force (this is wind blowing from high to low pressure)
Coriolis force (this turns wind to the right in the NH and left in the SH and causes the wind to flow parallel to isobars)
gravity (provides hydrostatic balance with the PGF in the vertical)
Friction (in the boundary layer you may see this as $\nu\nabla^2\mathbf u$)
The following is multiple choice question (with options) to answer.
A breeze is blowing across a field, growing stronger and stronger. The breeze becomes a storm of wind, moving rocks and breaking trees. This wind is likely the cause of | [
"evenly heated spaces",
"unevenly distributed heat",
"heated earth spaces",
"space heaters"
] | B | uneven heating causes convection |
OpenBookQA | OpenBookQA-523 | orbit, the-sun, earth
Notes:
It takes the Earth 365.256363004 days to revolve around
the Sun with respect to the fixed stars, but the time
between vernal equinoxes is slightly less (365.242190402
days) because the position of the vernal equinox moves
(precesses) with respect to the stars. Source:
http://hpiers.obspm.fr/eop-pc/models/constants.html
The Gregorian calendar's average day length of 365.2425
is much closer to 365.242190402 days than the Julian
calendar's 365.25 average day length, but it's still not
perfect. As noted in
Do solstices and equinoxes shift over time?
if we continue using the Gregorian calendar in the far
future, the equinoxes and solstices will drift
backwards. By 17090 (the limit of DE431), they will look
like this:
EQU 476198945887.238159 A.D. 17090-02-22 08:56:59
SOL 476207018540.040894 A.D. 17090-05-26 19:21:11
EQU 476214808218.146362 A.D. 17090-08-24 23:09:09
SOL 476222655067.609985 A.D. 17090-11-23 18:49:59
about a month behind their "regular" times.
MY EARLIER PARTIAL ANSWER FOR REFERENCE:
Since HORIZONS (http://ssd.jpl.nasa.gov/?horizons) and SPICE (http://naif.jpl.nasa.gov/naif/tutorials.html) can compute the ecliptic and solar position back that far, it should be possible to compute equinoxes and solstices with reasonable accuracy. However, I haven't been able to find a site that actually lists these dates (I'm pretty sure USNO did this at one point, but I can't find their list). Other possibly helpful sources/questions:
The following is multiple choice question (with options) to answer.
How many times per 365.3 days does an equinox occur? | [
"3",
"1",
"2",
"4"
] | C | an equinox occurs twice per year |
OpenBookQA | OpenBookQA-524 | solutions, gas-laws, vapor-pressure
According to the picture, which has three complete lines and one partial line, the straight line going from 0,0 to 1,1 designates the molar composition of the liquid (the independent variable). Then the two curved lines above it are the connected dots of measurements of the vapor-phase composition at approximately 1 atmosphere pressure and the boiling point of the mixture (which is varying, but called constant because it is uniformly the boiling point). The data were obtained by boiling the mixtures and taking vapor samples in an equilibrium still (Ref 2).
All the colored dots lie above the straight line, indicating that the vapor is enriched in hexane, or the liquid is impoverished in hexane, so hexane-benzene attraction not only does not keep the hexane in the liquid, but forcing hexane into benzene seems to be somewhat unattractive.
The partial line (a few red dots between 0.9, 0.9 and 1,1, at ~5 atmospheres pressure is about 60ºC hotter than at 1 atm, and does not add anything more to the conclusion. It was shown that enrichment of the vapor (in hexane) ceased at about 3.5 mole % benzene (Ref 2). (Note than on the graph, 0,0 corresponds to all benzene, which has the higher boiling point (80.1º vs 69º for n-hexane)). It had been thought that hexane and benzene formed a constant-boiling mixture at ~2.5% benzene in hexane, but this was disproven. It's just very difficult to get all the benzene out of n-hexane.
In a way, this suggests that there is an interaction between benzene and n-hexane, but only at very low concentrations of benzene, perhaps not well described by Van der Waals interactions. Maybe a little bit of benzene causes the n-hexane molecules to rearrange and use up their packing space more effectively.
Ref 1: http://www.ddbst.com/en/EED/VLE/Images/VLE%20Benzene;Hexane_002.png
Ref 2. https://pubs.acs.org/doi/abs/10.1021/ie50283a006
The following is multiple choice question (with options) to answer.
What happens when hexane's temperature goes above 70 degrees celsius? | [
"It melts",
"it sublimates",
"it boils",
"It freezes"
] | C | boiling is when liquids are heated above their boiling point |
OpenBookQA | OpenBookQA-525 | agriculture
The primary cereals for making bread are wheat and rye, while barley and oats may be mixed in. Historically significant portions of the rural population of Europe were sustained by cereal-based food in the form of gruel and porridge rather than by bread, especially prior to the introduction of the potato. Barley can be consumed in the form of pearl barley and groats and oats in the form of oatmeal. Especially in cool and humid climates not very suitable for cultivating wheat and rye, oats were once commonly cultivated and consumed. When Samuel Johnson wrote his dictionary, he famously defined oats as: "A grain which in England is generally given to horses, but in Scotland supports the people." A major historical and modern use of barley has been as malted barley, the main ingredient in beer brewing.
In the case of Finland it is interesting to note how late the transition from slash-and-burn agriculture to the use of permanent fields occurred. According to Teija Alenius, Environmental change and anthropogenic impact on lake sediments during the Holocene in the Finnish − Karelian inland area, Ph.D. thesis, University of Helsinki, 2007 (online)
The following is multiple choice question (with options) to answer.
Which of the following crops was the first staple in the human diet? | [
"wheat",
"barley",
"corn",
"rice"
] | A | humans eat crops |
OpenBookQA | OpenBookQA-526 | homework-and-exercises, radiation
Title: light beams of the sun
We receive sunlight on earth surface. What type of light beams are these?
Random/Parallel/Converging/Diverging
I think it should be Diverging as Sun is radiating these beams away. But in one book, answer is given as Random, in another it's Parallel. It is difficult to answer this question. An EM wave is generated by vibrating charges and nuclear reactions. Sun is full of vibrating charges and nuclear fusions. Because of this full range of frequencies are emitted. At distances close to sun we observe the directions of waves to be random. But at far away distances the direction of waves seem parallel. Since only parallel waves can have constant separation between them. Converging and diverging waves become distant at longer distances.
The following is multiple choice question (with options) to answer.
An example of how sunlight is a source of light from the sun is | [
"weather being variable",
"raising temps",
"windmills producing energy",
"frogs croaking"
] | B | the sun is a source of light called sunlight |
OpenBookQA | OpenBookQA-527 | ocean, climate-change
During the 20th century, sea level rise was estimated from tide-gauges, which raises the problem of 'are we measuring rising sea or sinking land?' For the last decade or so we have been able to measure absolute mean sea levels by satellite. That is, independent of land levels. Now we can re-evaluate old data, and come up with 'real' average rates of rising sea level. They turn out to be about 2.5 +/- 1.5 mm/year for most of the last century. Now they have accelerated to more than twice that amount. See, for example:
https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level
This is the global average, and yes, there are all manner of positive and negative anomalies. Now consider sediment displacement. Measuring the global sediment flux from rivers to oceans is extraordinarily difficult, for reasons which would take several pages to explain. But of the diverse range of estimates the consensus seems to be between 20 and 60 Gtonnes per year for the world's major rivers. Leaning towards the upper bound, and adding in a factor for the minor rivers, and assuming an average sediment density of about 2.5, we arrive at about 40 billion cubic metres of sediment entering the oceans each year. There are about 360 million square kilometres of ocean, so on average, the annual increase in ocean sediment is about 1.1 mm. In reality, this is an upper bound with the a more realistic estimate being about 0.6 mm. So, even without taking oceanic subduction into account, the observed sea level is at least an order of magnitude more than can be accounted for by sediment displacement. Or to answer your question, no, the ocean floor isn't rising at any rate that we can measure. Conversely, sea level is rising at a rate that is consistent with thermal expansion of the ocean surface, combined with nett global ice melt.
The following is multiple choice question (with options) to answer.
The amount of water in the ocean compared to fifty years ago is | [
"fluctuating",
"larger",
"smaller",
"the same"
] | B | as the amount of water in a body of water increases , the water levels will increase |
OpenBookQA | OpenBookQA-528 | geophysics, sedimentology, glaciology, topography, isostasy
Are there any other reasons? What are the relative proportions in magnitude of these factors? Forming of coastline
During the last ice age, the North Sea was dry. When the ice melted sea levels slowly started to rise again and due to tides and currents
a barrier of dunes was formed along what approximately is today's coast line. This created an area of land that fell dry during ebb-tide and flooded during high tide (this can still be seen in the 'Waddenzee' in the North of the Netherlands where you can walk to some of the islands during low tide). The big rivers that flow through the Netherlands brought in more sand, slowly keeping larger parts of the land dry.
Isostatic rebound
During the ice age, the surface of Scandinavia was pushed down. After the ice melted it started to rise again and pushed the Western and Northern part of Netherlands down. Strangely enough the Southern and Eastern parts of the Netherlands are rising, so it seems the Netherlands is tilting.
I'm not sure how large the isostatic effect has been, but we know that the North of the Netherlands is still going down with about 2cm per century (source in Dutch).
Human influence
I know you've asked for non-anthropogenic causes, but I'm going to include this anyway because it seems human influence has had a much bigger effect on elevation than the isostatic rebound.
In the 11th century the Dutch started to actively shape the land by building dikes and later also by using wind mills to pump out water. The Flevopolder is an example of a large part of land that has been created by the Dutch in the 1950s and 60s. When groundwater levels became lower the moors settled and started oxidizing. Researchers think that the settling and oxidation of moors today is responsible for up to 15mm decline per year (source in Dutch).
Additionally in the 16th and 17th century a lot of peat was removed from the moors and used as fuel. Peat removal created new lakes, but some of those lakes were pumped dry later and were used as farmland. Also, the weight of dikes and houses on moors still cause subsidence today in areas in the West.
In the Northeastern part of the Netherlands gas extraction has also caused local elevation drops of up to 30cm (source in Dutch) in the last 40 years.
Other sources (all in Dutch):
The following is multiple choice question (with options) to answer.
Heat from the sun, waves crashing down, and huge storms all wail on a large boulder at the shore. After a few hundred years, where the boulder stood is now | [
"earth",
"trees",
"corn",
"cats"
] | A | soil is formed by rocks eroding |
OpenBookQA | OpenBookQA-529 | entomology, invertebrates
Title: Selection for less efficient egg transfer in Human Botfly life cycle I have heard that the Human Botfly transfers its eggs through other invertebrates, and it strikes my curiosity that if an insect could simply land on its host directly to deposit its eggs, then why have intermediate hosts?
I have speculated that the vectors may be better specialized for penetrating hosts, and that penetrating hosts may be difficult, or that approaching hosts is risky. Another speculation on my part is that the Human Botfly may be filling a niche where it does not need to compete. In multi-host complex life cycles (CLCs), an intermediate host often aids in the dispersal of offspring.
In general terms, an animal, say a botfly, have an ultimate "purpose" or 'goal' to spread their genetic information as much as possible. This could mean producing a large number of offspring and hoping some survive or it could mean having one offspring, investing a lot of energy and ensuring it does survive. Regardless, spreading genetic information often requires offspring to disperse (or be spread) a great distance, which may allow the individuals' genetic information to dominate an new region.
In the case of botflies, having an intermediate host means the genetic information can be spread a great distance.
If you're looking for a more thorough explanation of complex life cycles, this paper describes it well. There is also this site more specific to the botfly which is not peer reviewed, but well-researched and descriptive.
The following is multiple choice question (with options) to answer.
What kind of insects lays eggs during the adult stage of its life cycle? | [
"All",
"large",
"queen",
"Male"
] | C | a female insect lays eggs during the adult stage of an insect 's life cycle |
OpenBookQA | OpenBookQA-530 | zoology, species-identification, ornithology, behaviour
Title: What is this crow eating, and is it a common part of the corvid diet? Here's a picture (by Rob Curtis) of a crow carrying and eating the corpse of what looks a bit like a small hawk or falcon:
Other pictures clearly show the crow is eating the dead bird. This image shows the underside of the head and beak; this one shows its legs, which are grayish.
What bird is being eaten?
Is this bird a usual part of the corvid diet? Or did the crow just opportunistically scavenge a dead bird? Crows are omnivorous, and will eat almost anything they find or can kill.
In this case the prey looks like a Yellow-Shafted Flicker.
The following is multiple choice question (with options) to answer.
Eagles eat | [
"hawks",
"flying insects",
"plants and grains",
"small burrowing mammals"
] | D | eagles eat rabbits |
OpenBookQA | OpenBookQA-531 | However, we count some of the cycles several times. Firstly, we distinguished the starting point $v_0$, which for a given cycle can be chosen in $k$ ways. Secondly, we distinguished an orientation, which for a given cycle can be chosen in two ways. Hence, each cycle is counted $2k$ times, and $T = n^{\underline{k}}/2k$.
Finally, we find: $$\mathbb{E}(X) = \frac{n^{\underline{k}}}{2^{k+1}k}.$$
• There are slight errors in the above. You fix v0 but you have n choices. Also you could have start from v1 or v2 or ... vk. Thus T = n(n-1)...(n-k+1)/2/k. Another way to prove it is: - you have binomial(n,k) ways to choose the k vertices - and (k-1)!/2 ways to label the k-cycle - each edge of the cycle exists with probability 1/2 In total you find the same result – user139226 Mar 31 '14 at 9:50
• @jojopil: Thanks for pointing this out! Corrected. – Jakub Konieczny Mar 31 '14 at 15:38
A probably simpler way to obtain the above result (as explained in comment by user139226).
Let $X$ be the random variable denoting the number of undirected cycles of length $k$. Let $X_{\left\{ V_i \right\}_{i = 1}^{k}}$ be the indicator random variable that the subset of verticies $\left\{ V_i \right\}_{i = 1}^{k}$ is a cycle of length $k$.
If $p \in [0, 1]$ is the probability that there is an edge between a pair of vertices (in this case $p = \frac{1}{2}$), then $P(\left\{ V_i \right\}_{i = 1}^{k} = 1) = p^k$. Now:
The following is multiple choice question (with options) to answer.
what characterizes a cycle | [
"a steady recurrence",
"none of these",
"a stagnant pattern",
"a circle shape"
] | A | a cycle happens repeatedly |
OpenBookQA | OpenBookQA-532 | soil-science
Title: How does humanure make soil "fluffier"? This BBC article says biosolids make soil "fluffier", among other benefits. How?
Adding humanure also changes soil structure, making it more resilient, preventing erosion and balancing out moisture, says Moss. It makes dirt fluffier, so water passes through easier. Conversely, in drought conditions, this also helps it retain water. The less compact soils are also softer, enabling seedlings to take faster and grow stronger roots, producing better yields. What are Biosolids and how do they work?
a biosolid is a product of the sewage treatment processes and is a semi-solid sludge of organic matter, nutrient-rich organic compounds. Here I list several reasons as to why biosolids would make the soil 'fluffier' and and better
As I said earlier biosolids are typically made out of organic matter, organic matter is carbon-based and biosolids are usually biological material (decomposed feces, urine and et cetera).
If you are not familiar with the normal decomposition processs it is a biological material (banana, apple, feces and et cetera) that is decomposed by microbes, molds, fungi and etc
biosolids are biological and/or organic material so what I just stated above applies to biosolids as well
Think of what you flush down a toilet or what goes down a sewer drain, are those things carbon based and biological? (human feces is an organic-compound and it goes in the sewers)
So now we know that biosolids are like other organic-compounds, how does this maker the soil fluffier. When something undergoes decomposition it turns into fresh brand-new soil, and quite obviously this new soil would be much more higher-quality and better than over-used old soil.
Here it states that organic material in a landfill produce gases due to decomposition so it makes sense that the same process would happen underground where microbial decomposition can release gases in the soil thus making the soil fluffier
So I can conclude that biosolids do, in fact help soil and make it fluffier and better.
The following is multiple choice question (with options) to answer.
Organic matter in soil can be increased by | [
"digging up flowers from the soil",
"skunks spraying their scent on the soil",
"the dead body of a mouse breaking down",
"animals eating crops planted in the soil"
] | C | decomposition increases amount of organic matter in soil |
OpenBookQA | OpenBookQA-533 | species-identification
Title: What bird / animal has this call? USA MA NE
I have a bird / animal coming to the trees in the backyard making this call (see link to audio file), which does not really sound like a bird - it's fairly low frequency. I have not seen it. Sometimes it sits in a young tree, where you can almost see through to the trunk. But I cannot make it out, so it's not very big (like a turkey). It comes at late afternoon and stays around until ~11PM. It switches trees fairly quickly, so I assume it can fly. The call is always the same. Sometimes another one of its kind answers.
Bird_animal_call_mp3
You don't need dropbox. Ignore "suspicious link". Close login popup. Click download arrow. Direct download.
I added a Soundcloud link:
Bird_animal_call_mp3 It is a grey tree frog's mating call. See youtube link:
Grey tree frog mating call
Source for finding the answer: Audubon Society
The following is multiple choice question (with options) to answer.
To attract birds to your yard | [
"erect a large menacing scarecrow",
"destroy all your flowers",
"cut down all trees big and small",
"put out seeds in an easily accessible dish"
] | D | feeders attract animals to a location |
OpenBookQA | OpenBookQA-534 | human-biology, reproduction
Title: Why are animal births not taken as seriously as human births? When humans give birth, more than often medical assistance is needed. Others gather around and frantically look for any way to help. But when an animal gives birth, it is usually seen as a moment where you give the female its space and let the birth occur naturally and without any assistance. The animal is of course in serious pain just as a female human but this is more than often not taken into account. Why is it that animal births are not taken as seriously? Our heads are bigger.
There's some debate on the issue, but in essence, human brains, and therefore heads, are very large relative to our body size. This is handy for all the intelligent things we like to do, but can be rather painful during birth. Because we walk upright, the size of a newborn's head is actually a non-trivial fact during the birthing process. There are two major implications.
The first is that human birth hurts. You can watch the birth of other animals and they seem to brush it off, but for humans, forcing that huge head through a relatively small birth canal is difficult. Evolution has (supposedly) limited the size of the hips because, while that would allow an easier birthing process, it would negatively impact our ability to walk. As such, it has to hurt.
Secondly, in order to make the process easier, humans rotate during birth. The end result is that, unlike even other closely related primates, humans come out backward in a way that is very difficult for a birthing female to attend to. This almost requires having another person or two on hand to help out. This would, of course, be a huge reinforcement for social connections.
A few books I know of touch on this. Up From Dragons deals with the brain size/hip size issue and The Invisible Sex talks about rotation during the birthing process and the social implications.
The following is multiple choice question (with options) to answer.
If a kitten is unable to nurse from birth | [
"it will cry",
"it will expire",
"it will sleep",
"it will vomit"
] | B | lack of food causes starvation |
OpenBookQA | OpenBookQA-535 | earth, amateur-observing, fundamental-astronomy
Title: Does weight influence Earth's spin? If put enough weight on a particular point on Earth's surface disturbing the balance between hemispheres, is it possible that the Earth's spin could change like an unbalanced spinning top? The Earth does spin like an unbalanced top. The Earth's rotation axis is not fixed. It instead moves in a complex manner due to a combination of external torques exerted by the Moon and Sun, a torque-free nutation due to the oblate shape of the Earth, and also due to changes on and in the Earth.
The torque-induced motions are called precession and nutation, distinguished by period. The largest and slowest of these motions is the axial precession. This causes the Earth's rotation axis to trace out a cone over the course of 26000 years.
(source: nasa.gov)
The torque-induced nutations are also cyclical motions induced by the Moon and the Sun. These are much smaller in magnitude and have a much shorter period. The largest of these has a magnitude of about 20 arc seconds and a period of 18.6 years. All other nutation terms have much smaller magnitude and have shorter period.
The torque-free nutation would have a period of about 305 days if the Earth was solid. The oceans, the atmosphere, and the outer core alter this. The Chandler wobble has a period of about 433 days and a magnitude of less than an arc second. Because the Chandler wobble isn't as predictable as are precession and nutation, it's lumped into a catch-all category called "polar motion." The redistribution of water over the course of a year (e.g., snow on Siberia in the winter but not in the summer) results in a yearly component of the polar motion.
There are lots and lots of other factors, all small. Polar motion is observed after the fact.
The following is multiple choice question (with options) to answer.
Three hundred and sixty five turns of the earth is | [
"double half a calendar year",
"a very long time",
"almost half of a lifetime",
"more than two years"
] | A | one year is equal to 365 days |
OpenBookQA | OpenBookQA-536 | acoustics, air, displacement
You can see the derivation of the above at http://www.insula.com.au/physics/1279/L14.html and if you look for problem # W4 on that page you will find the calculation for a pressure level of 28 mPa at 1 kHz giving 11 nm displacement amplitude. Given that the limit of detectable sound level is about 1000x smaller, my numbers above are quite reasonable.
So the real answer to your "headline" question ("how much air needs to be displaced to generate an audible sound") is
The equivalent of one layer of atoms is more than enough
Impressive, how sensitive the ear is. And bats and dogs have even better hearing, I'm told.
The following is multiple choice question (with options) to answer.
How essential is air for animals? | [
"it is optional",
"it is necessary",
"it is useless",
"it is unknown"
] | B | an animal requires air for survival |
OpenBookQA | OpenBookQA-537 | everyday-life, material-science
Title: Why can we tear a newspaper neatly one way but not the other way? When I try to tear the newspaper from top to bottom (or bottom to top), it's torn pretty neatly and like a line, but when I try to tear it from side to side, it goes all over the place and tries to lead the tear towards the top or bottom.
Why does this happen? Newspaper is made out of cellulose fibres (linear unbranched ones) bonded entangled together.
The fibre structure is anisotropic. The orientation of most of the fibres is along the direction of the movement of the machine.
In the direction of this orientation, it is relatively easier to tear a newspaper because it's just a matter of prying two fibres apart. (without significant tearing of fibres)
In the direction perpendicular to this, fibres have to be broken to tear the paper, and this requires a greater force.
The same asymmetry account for why tears are neat/messy depending on the direction you take.
If a piece of paper was isotropic, with random orientation of fibres, tearing would roughly take the same effort in any direction.
The following is multiple choice question (with options) to answer.
Ripping a paper in half | [
"alters the shape of the paper",
"leaves the paper unchanged",
"enlarges the piece of paper",
"makes the paper into its gas form"
] | A | tearing an object changes that object 's shape |
OpenBookQA | OpenBookQA-538 | human-biology, breathing
Our lungs work off of pressure. Specifically our lungs inflate by using "negative pressure" (a word I've always hated). The pressure is not actually negative it is simply lower than the surroundings. Since there is less air in your lungs the air from the atmosphere rushes in because the pressure is higher outside your lungs. This is Boyle's Law (not the pressure outside being higher, but what happens when your lungs expand). Where an increase in Volume means a decrease in Pressure (if all else remains unchanged). In fact plants pull water up using negative pressure.
However to push out the air from our lungs we supply pressure using our muscles that overcomes the outside pressure and forces the air out.
The reason you feel your breathing change is because when that train passes by you correctly observed the strong gust of wind. This gust of wind has some force behind it that normally is not in the air you are breathing from the atmosphere. It has more force which increases the air's velocity. This actually decreases the pressure, but there's no need to get into that here (Bernoulli's).
The reason it feels like your body is "fighting to breath" is because the air is traveling in a direction with some force that you need to overcome by opening up your lungs just enough to "suck" the air in with negative pressure. This is more than the pressure you usually need to produce in order to breath in air that is "still".
What is funny to think about is we don't really have a muscle that "pulls" air in, even though it feels like you are actively doing that. The air actually rushes in on its own. All you do is expand your rib cage, which your lungs are attached to (look up on how, it's actually pretty cool), thereby making inhalation occur.
Now an interesting question for you to ask yourself is why is cold air harder to breathe?
The following is multiple choice question (with options) to answer.
Breathing is when the lungs convert oxygen from inhaled air into | [
"oxygen dispersed from respiratory bronchioles through air sacs to hemoglobin proteins",
"Glucose particles in the blood",
"nitrogen oxide in the blood",
"carbon monoxide in the blood"
] | A | breathing is when a lung converts from oxygen in air into oxygen in blood |
OpenBookQA | OpenBookQA-539 | climate, solar-terrestrial-physics
Title: Why is March colder than September in Northern Hemisphere? Forgive my ignorance of the subject but I was always wondered about the exact reason of this phenomenon.
Vernal equinox happens around March 20, whereas autumnal equinox happens around September 22, so wherever you are in Northern Hemisphere, the length of the day, and consequently the amount of solar energy that reaches the place should be almost the same.
However the average temperatures differ widely, for example Toronto has average temperatures of 2°C to 6°C on March 20th, and 14°C to 19°C on September 22nd. So around 12°C difference [link].
So obviously there is some sort of temperature inertia, as temperatures seem to experience a delay in responding to changes in day length.
What is the main reason for it? Is it effect of sea ice or snow-covered land albedo? Energy stored in oceans? Energy absorbed by melting snow and ice? The phenomenon is called seasonal lag.
There's a more extensive answer elsewhere on this site but the basic idea is that temperature lags behind insolation by several weeks, because it takes time to change the mean temperatures of the land, the atmospehere, and especially oceans change their mean temperature. This diagram tries to show the lag, along with various ways of reckoning the seasons:
The following is multiple choice question (with options) to answer.
frozen rainfall falling leaves the northern hemisphere a carpeted | [
"grey",
"yellow",
"white",
"off white"
] | C | cold environments are usually white in color from being covered in snow |
OpenBookQA | OpenBookQA-540 | tsunami, solitary-waves
Which equations govern the surface profile of a tsunami? Has this model been tested against satellite measurments? Short answer: Tsunami models use the shallow-wave mathematical approach, because their wavelength is usually much larger than the relevant water depth determining their propagation.
Long answer:
Tsunamis are often called 'tidal waves' to highlight the idea that their characteristic time response is closer to tydes than to the standard wind waves we are used to see in a beach. The full spectrum of water wave periods is shown in this figure (tsunamis being classified as long-period waves, together with waves caused by meteorological events):
Classification of the spectrum of ocean waves according to wave period. Redrawn from Figure 1 in: Walter H. Munk (1950) "Origin and generation of waves". Proceedings 1st International Conference on Coastal Engineering, Long Beach, California. ASCE, pp. 1–4.
This image shows that the wave frequency depends on the cause behind the perturbation of the water surface.
Oceanographers generally treat ocean waves as free surface waves in an ideal fluid [2].
Mathematically, tsunamis are surface gravity waves approached as shallow-water waves (see chapter 4.1.5 in here), meaning that the wavelength λ > 20H (H being the water depth). The involved shallow-water-wave mathematical approximations oppose to the deep-water waves (λ < H, see section 4.1.4 in the same [ref 3]).
Whereas for shallow waves the wave frequency and the wave speed are (ref. 3):
$ω = \sqrt {g k 2H}$ with $k = 2\pi / \lambda$
$c = \sqrt {g H}$
for deep-water waves, instead:
$ω = \sqrt {g k}$
$c = \sqrt {\frac{g \lambda}{2\pi}}$
As the wave approaches the shore and H decreases, the wave velocity decreases and energy is preserved by increasing the wave amplitude.
Detailed information here: 3.
The following is multiple choice question (with options) to answer.
Tsunamis | [
"have little impact on the environment",
"can be easily halted",
"can rearrange coastal shorelines",
"can encourage economic growth"
] | C | natural events usually cause changes to Earth 's surface |
OpenBookQA | OpenBookQA-541 | physical-chemistry, thermodynamics, heat, mixtures
Where does this come from and what are the assumptions involved in treating it as an ideal mixture?
What deviations from this are observed in non-ideal mixtures? Can you easily predict the deviations based on the mixture and/or predict the actual specific heat capacity? Suppose you have $n_1$ mole of A and $n_2$ mole of B. If they are at temp. $T_1$ and you want to raise the temp. to $T_2$ then the amount of heat you need to add is
$$\Delta H~= n_1 \times c_{pA} \times \Delta T + n_2 \times c_{pB} \times \Delta T$$
$$\Delta H~= (n_1 \times c_{pA} + n_2 \times c_{pB}) \times \Delta T$$
$$\Delta H~= (n_1 +n_2)\times \frac{(n_1 \times c_{pA} + n_2 \times c_{pB})}{(n_1+n_2)} \times \Delta T$$
$$\Delta H~= n_{total} \times(y_1 \times c_{pA} + y_2 \times c_{pB}) \times \Delta T$$
$$\Delta H~= n_{total} \times c_{p,avg} \times \Delta T$$
So basically you are not losing any information in case of ideal situation where molecular interaction of two different species has no effect on each other's heat capacity. But from statistical mechanics we know,
$$C_v=\frac { <E^2>-<E>^2}{k_B \times T^2}$$
Now if we solve the schrodinger equation for individual species, we must include an extra potential energy term to account the interaction from other species, which in turn will result in fluctuation of $C_v$ from it's previous value.
The following is multiple choice question (with options) to answer.
An example of a mixture is | [
"light",
"a molecule",
"terra cotta",
"gold"
] | C | An example of a mixture is clay mixed together |
OpenBookQA | OpenBookQA-542 | wildfire
There are detailed satellite imagery with PM2.5 monitor overlay at Aerosol Watch, if you would like to see how the event progressed through time.
The following is multiple choice question (with options) to answer.
wildfire occurs when | [
"being environmental is considered hot",
"someone smokes near a forest",
"condensed tree areas are ablaze",
"tree patterns are similar to fire"
] | C | wildfire is when a forest catches fire |
OpenBookQA | OpenBookQA-543 | population-dynamics, population-biology
Title: Spread of a benign virus in a population over time This is a somewhat difficult (for me) population dynamics question and I wonder if someone with experience in this area could suggest a reasonable approach?
My simplifying assumptions: As a gross oversimplification, let p(k) be the world's population at generation k, and assume a smooth exponential curve that models p(k) from $k=0$ at 10,0000 B.C.E to generation $k=600$ in 2000 C.E. A generation is 20 years, and in acc. with this Wiki there are about 4 million individuals at $k=0$ and 6070 million at $k=600.$
(Of course the exponential model is bad, as world population growth appears to have been sluggish before recorded history.)
Now assume a benign virus infects 120 individuals in $k=0.$ It benignly infects all individuals who have at least one infected parent. Perhaps unimportantly, it also continues to infect 30 new individuals per million in each generation (because its found in the soil), but would not infect those already exposed.
Call infected individuals II and non-infected NI. They are indistinguishable without clinical tests--which are not done, since the virus is harmless. Since II individuals are almost certain to mate with NI individuals, in earlier generations, the number of II will grow very quickly. For a time the growth rate of II will exceed that of p(k). At some point it will be unlikely that an II individual will encounter an NI mate, however a few NI persons will still pair with NI mates--for a while.
My question is, after 600 generations, what is a reasonable estimate of the percentage of II in the population? Is is possible that there would be any NI individuals left? Or would we have some sort of dynamic equilibrium between II and NI in which (I think) the former would strongly dominate?
FWIW, the population growth model is $p(k)=4e^{0.012 k}$ with $p(k)$ in millions. For simplicity, I denote the population of non-infected individuals by $N$ and the infected ones by $I$.
Model without soil infection
The following is multiple choice question (with options) to answer.
Which of the following has a population of zero? | [
"Merriam's elk",
"bison",
"llama",
"whooping crane"
] | A | if a population decreases to zero then that organism is extinct |
OpenBookQA | OpenBookQA-544 | earth, amateur-observing, fundamental-astronomy
Title: Does weight influence Earth's spin? If put enough weight on a particular point on Earth's surface disturbing the balance between hemispheres, is it possible that the Earth's spin could change like an unbalanced spinning top? The Earth does spin like an unbalanced top. The Earth's rotation axis is not fixed. It instead moves in a complex manner due to a combination of external torques exerted by the Moon and Sun, a torque-free nutation due to the oblate shape of the Earth, and also due to changes on and in the Earth.
The torque-induced motions are called precession and nutation, distinguished by period. The largest and slowest of these motions is the axial precession. This causes the Earth's rotation axis to trace out a cone over the course of 26000 years.
(source: nasa.gov)
The torque-induced nutations are also cyclical motions induced by the Moon and the Sun. These are much smaller in magnitude and have a much shorter period. The largest of these has a magnitude of about 20 arc seconds and a period of 18.6 years. All other nutation terms have much smaller magnitude and have shorter period.
The torque-free nutation would have a period of about 305 days if the Earth was solid. The oceans, the atmosphere, and the outer core alter this. The Chandler wobble has a period of about 433 days and a magnitude of less than an arc second. Because the Chandler wobble isn't as predictable as are precession and nutation, it's lumped into a catch-all category called "polar motion." The redistribution of water over the course of a year (e.g., snow on Siberia in the winter but not in the summer) results in a yearly component of the polar motion.
There are lots and lots of other factors, all small. Polar motion is observed after the fact.
The following is multiple choice question (with options) to answer.
The Earth spins around and around, and in order to finish one cycle of this spinning | [
"two days must pass",
"a week must go by",
"the Earth must slow down",
"a seventh of a week must pass"
] | D | a Rotation of the Earth on Earth 's axis takes 1 day |
OpenBookQA | OpenBookQA-545 | resonance, vibrations, coupled-oscillators
Title: String Vibrations Interesting thing I noticed just now playing my ukulele.
For those who don't know how a ukulele works, it has four strings: a high G followed by a lower C, E, and A. Holding down frets causes the strings to play progressively higher-pitched notes. Now, it is possible for two or more strings to play the same note. I've noticed that when this happens, playing one string will cause the others of the same pitch to vibrate, even without actually playing them. However, it's only when they are exactly the same note. If it's not the same note, it doesn't vibrate (at least not perceptibly). Why? If it's caused by the vibration from the string spreading outward, why would it matter what pitch the strings are relative to each other?
Perhaps it's a property of the nylon in the strings? After noticing this, I checked on my steel-stringed acoustic guitar, which definitely does not (perceptibly) do this. The sound of a ukulele (or any similar instrument - guitar, violin, etc) does not come from the strings themselves, but from the whole body of the instrument vibrating and moving the air which is in contact with it.
The vibrations are transmitted from the strings to the body of the instrument mainly through the bridge.
If you stop two strings so that they produce the same pitched note, the vibration of the bridge will cause both strings to vibrate if you pluck one of them.
This will also happen on an acoustic guitar, but in an electric guitar the sound is not physically produced by the body of the instrument vibrating. Instead, by magnetic pickups sense the vibration of the steel strings and the electrical signals are then amplified and sent to a loudspeaker.
The same effect happens in instruments like the piano, but the steel strings are at a higher tension than in plucked instruments and there is no visible vibration of the strings (except perhaps for the lowest bass notes) in normal playing.
The following is multiple choice question (with options) to answer.
When I play a violin the strings and create sound through | [
"A new word",
"A quake",
"Pens",
"Sweat"
] | B | plucking a string can cause that string to vibrate |
OpenBookQA | OpenBookQA-546 | measurements, discrete
Title: Why are 'units' of measure discrete? Why do we measure quantities like length, time, mass in terms of a discrete quantifiable unit (for eg: length in metres or planck lengths, if one scales down to that level) ? Is it possible to quantify physical dimensions as a continuous real entity? I'd really appreciate it if someone would kindly break this down for me and explain to me in the simplest way possible. I apologize if I cannot get my question through to the members of the community due to my lack of knowledge of technical terms: I am a mathematics undergraduate student, so kindly bear with me.
Edit:
Consider the unit of length. Bring two points A and B arbitrarily close, to say 1 planck unit. Now halve that distance (theoretically of course), and keep halving them such that they become closer and closer still. Do this arbitrarily many times. Note the distance is still not zero. But there is no quanta of measurement as it is much smaller that the quantifiable physical quantity. So how do we overcome this hurdle of defining length arbitrarily close without using quanta of measurement? You've either totally garbled your understanding of definitions or you've answered your own question.
By definition, a unit is something which is fundamentally non-continuous. A unit is either:
a) Something that is considered single and complete in itself. It is absolutely individual but can make up parts of a greater whole. In other words, it is an element, a building block upon which to consider other greater things.
b) A set quantity which is deliberately chosen as a standard in terms of which other quantities may be expressed. It then becomes convention and scaling occurs from there.
The following is multiple choice question (with options) to answer.
Measuring is a way to collect data; what is an example of this? | [
"pouring water into a gallon jug to save for later",
"pouring milk into a half cup to see how much is left",
"making sure that a blanket is warm enough for the night",
"noticing how long a cat's tail is"
] | B | An example of collecting data is measuring |
OpenBookQA | OpenBookQA-547 | evolution, zoology, adaptation
One answer that came to mind is domestic animals - the horse and dog in prehistory, the cat in ancient Egypt, etc. That seems too obvious on one hand, and on the other hand may not really be an answer, as there seems to be no indication that pre-domestic animals were endangered by humans in any meaningful way. Are there animals that have significantly adapted themselves to surviving as wild animals in human-influenced environments? Note: This is an answer to the last line of your question.
A classical example of animals adapting to the influence of humans on their environment is the adaption of the Peppered Moth.
Here is a brief summary:
The peppered moth was originally a mostly unpigmented animal (<1800). During the industrial revolution in the southern parts of the UK a lot of coal was burned. This led to soot blackening the countryside. Soon afterwards, a fully pigmented variety was first observed. Only a hundred years later, in 1895, this pigmented variety almost completely displaced the unpigmented variety.
It has been shown that the pigmentation is under strong selective pressure as birds hunt these moths. Since birds rely on their visual system to detect their prey, the variety that blends in with its environment (=camouflage) has a selective advantage over the variety that stands out.
As pointed out by Tim in the comments, since the 1970s there has been a rapid reversal with unpigmented animals being more abundant. As far as I understand, it is accepted that this reversal is due to a decrease in human induced air pollution leading to less sooty barks on trees which makes the unpigmented variety harder to prey upon.
Addendum: genetic basis of adaption
In a beautiful recent study, the causal mutation for the pigmented, or melanic, variety was identified: A ~9kb transposon insertion in the first intron of the gene cortex. The authors calculate that this mutation happened in the year 1819, a few years after the industrial revolution was in full swing. The interpretation is that due to sooty tree bark this mutation, causing pigmented moth, was under strong selection.
The following is multiple choice question (with options) to answer.
What impact does humans changing animals habits have? | [
"inimical",
"shameful",
"positive",
"happy"
] | A | humans changing animal habitats usually causes harm to those animals |
OpenBookQA | OpenBookQA-548 | astronomy, everyday-life, popular-science, climate-science
Title: Why is the summer, in the temperate latitudes, in average, hotter that the spring? It is common knowledge that the transition from the Spring to the Summer season occurs in the Summer Solstice when the "Sun reaches its highest excursion relative to the celestial equator on the celestial sphere" (as stated in Wikipedia).
It is also stated in Wikipedia' Summer page:
"Days continue to lengthen from equinox to solstice and summer days progressively shorten after the solstice, so meteorological summer encompasses the build-up to the longest day and a diminishing thereafter, with summer having many more hours of daylight than spring."
My question is: why is the summer, in the temperate latitudes, in average, hotter that the spring? A major part of the reason for this is due to the temperature of the ground. While the length of days in the Summer are effectively a mirror of those in Spring, you must take into consideration more than that.
When Spring commences in temperate climates, it is (usually) immediately preceded by winter. Due to the Winter, the ground and/or surrounding bodies of water are very cold. This has the effect of cooling the air for the first part of Spring while the ground/water begins to thaw/warm up. Furthermore, it takes much longer to warm or cool a body of water than a mass of air; even longer to warm or cool the ground and water. Therefore, as Spring progresses and the days become longer (also meaning the Sun is higher above the horizon, thus providing more heating power), the sunlight must first overcome the cooling effects of the ground and water bodies. Near the end of Spring - when the days are sufficiently long and the Sun is much higher above the horizon - you should notice the weather becoming hotter. This is because the ground and water has had time to warm up, which means it is not constantly cooling the air and making it feel colder.
When you then transition to Summer, the ground is already sufficiently warm but the days are still long and the Sun is still high in the sky. This means the Sun can heat the ground, water, and air even more and without any cooling effects. This allows the Summer temperature to be easily higher than that of the Spring temperatures. If Summer were immediately preceded by winter, you might notice the weather getting warmer much more quickly, but the average temperature would be very close to that of the Spring.
The following is multiple choice question (with options) to answer.
In a decade spring occurs | [
"three times",
"twelve times",
"ten times",
"twice"
] | C | each season occurs once per year |
OpenBookQA | OpenBookQA-549 | 1) Row 1: A-B, Row 2: C-D
2) Row 1: A-C, Row 2: B-D
3) Row 1: A-D, Row 2: B-C
4) Row 1: B-C, Row 2: A-D
5) Row 1: B-D, Row 2: A-C
6) Row 1: C-D, Row 2: A-B
Thus, for each group of 4 dogs chosen, there could be 6 teams. Therefore, the total number of teams that can be formed is 70 x 6 = 420.
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Re: Eight dogs are in a pen when a sled owner comes to choose four dogs to [#permalink]
### Show Tags
07 Oct 2017, 05:52
JeffTargetTestPrep wrote:
Bunuel wrote:
Eight dogs are in a pen when a sled owner comes to choose four dogs to form a sled team. If the dogs are to be placed in two rows of two dogs each and different pairings of dogs are considered different teams, how many different sled teams can the owner form?
A. 24
B. 70
C. 210
D. 420
E. 1,680
There are 8C4 = 8!/[4!(8-4)!] = (8 x 7 x 6 x 5)/4! = (48 x 7 x 5)/24 = 2 x 7 x 5 = 70 ways to choose 4 dogs from a total of 8 dogs. Once 4 dogs are chosen, let’s see how many pairings of two rows of 2 dogs are possible. Let’s say the 4 dogs are A, B, C, and D.
The following is multiple choice question (with options) to answer.
Some animals are housed | [
"in public exhibitions for viewing",
"in boxes for storage",
"in barrels for travel",
"in tents for sleeping"
] | A | some animals live in zoo exhibits |
OpenBookQA | OpenBookQA-550 | human-biology, mammals, lifespan, dogs, rodents
Gigantism:
Whilst the life expectancy for a species may be higher in general people with gigantism may live shorter lives than possible because of non-metabolic related reasons. For example many forms of gigantism are linked to hormones which promote cell division and growth which are also linked to forms of cancer.
The following is multiple choice question (with options) to answer.
Being stronger has what impact on a creatures health? | [
"bad impact",
"unexpected complications",
"minimum effect",
"good influence"
] | D | being stronger usually has a positive impact on an living thing 's health |
OpenBookQA | OpenBookQA-551 | thermal-conductivity
$$T_\text{interface}=\frac{\sum_i(k_iT_i/L_i)}{\sum_i (k_i/L_i)},$$
and so the heat flow is $q=A\frac{T_1-T_2}{\sum_i R_i}$, which holds generally for even $i>2$ if the end temperatures are taken as $T_1$ and $T_2$. Note that the thermal resistances (not the thermal conductances $1/R_i$) end up adding.
The following is multiple choice question (with options) to answer.
Thermal conduction is | [
"room temperature water sitting on a counter",
"a dog's paws touching summer scorched pavement",
"cake pans stacked in an oven",
"ice touching ice in a freezer"
] | B | when a cooler object touches a warmer object , thermal conduction occurs |
OpenBookQA | OpenBookQA-552 | earth-history, mass-extinction, geobiology, evolution, ecology
Title: Why haven't weeds overtaken the entire planet? Given how rapidly weed plants spread and grow, choking out all other plant life, how come after millions of years we haven't ended with forests full of thistle or pokeweed, as opposed to pines or oak trees? A weed is just a plant where you do not want it. Totally a matter of context. Tumbleweeds are non-native, introduced centuries ago. I assume you mean the invasive species of plants that have been spread by humans and are disrupting ecologies throughout most of the world
Until recently, these plants we consider weeds were limited in their range to home environments simply by geographic barriers and surrounding unfriendly environments. And the natural consumers, parasites and competitors in the home environments had adjusted to these plants and kept them in check.
When non-native plants are introduced into a new environment by humans, most of them do not thrive, but occasionally a plant is wildly successful. Eventually the potential consumers, parasites and competitors in that new environment will adjust through evolution. But the tragedy is that many or most of the original species will be destroyed before that balance is restored in a new, way more simplified form. The landscape itself may be totally changed. Removal of a key original species can cause great change too: How Wolves Change Rivers.
Not only will many ecologies be reduced to much simpler versions, even if they eventually conquer the invasive plant, those simplified ecologies will closely resemble each other, if their geography is similar, even if on the other side of the world. If humans were to totally stop transplanting invasive species (collapse of civilization?), diversity would return after millions of years. We know this from Extinction Events.
So to answer you question, weeds before human intervention generally did not take over in their home environments because the potential weeds and their natural consumers, parasites and competitors all evolved together in a quasi-equilibrium. Now, however, most ecologies throughout the world are out of equilibrium because of environmental change and/or invasive species. This will inevitably lead to simplified, usually less robust, weedy ecologies throughout the world. That reduction in diversity might as well be considered a permanent situation compared to the timescale of civilization.
The following is multiple choice question (with options) to answer.
New plants sprang up everywhere seeds were taken by | [
"cool breezes",
"magic",
"luck",
"demons"
] | A | plant requires seed dispersal for reproduction |
OpenBookQA | OpenBookQA-553 | nuclear-physics, astrophysics, solar-system, metallicity
How many times has the stuff of the Sun been recycled?
How many times has the "stuff" in our solar system been recycled from previous stars?
Let me mention that it's not a problem for the heavy material to spread across large distances of the Cosmos. For example, an exploding supernova shoots most or all the matter by the speed 1% of the speed of light. So in 400 years, the material from the Sun - if it went supernova (it won't) - reaches Proxima Centauri and in less than 100 million years, it may reach almost any point in the Milky Way. Even the Solar System is moving at speed of 0.1% of the speed of light which is enough to move matter by light years in thousands of years. It's silly to imagine that the material had to wait on the same place from an "ancestor star", being saved for some humans on some Earth.
It may be useful to list all processes of stellar nucleosynethesis, not only those linked to uranium:
pp-chain / CNO cycle / α process / Triple-α / Carbon burning / Ne burning / O burning / Si burning / R-process / S-process / P-process / Rp-process
The following is multiple choice question (with options) to answer.
Recycling happens | [
"when coal is turned into heat energy",
"when fossil fuels are used by cars",
"when Styrofoam plates are turned into trash",
"when old Pepsi bottles are turned into t-shirts"
] | D | An example of recycling is using an object to make a new object |
OpenBookQA | OpenBookQA-554 | climate-change, geography, rivers, rainfall, agriculture
Today Climate change and its consequences are some of the biggest challenges facing Humanity, with water scarcity being the big factor in Sub-Sahara Africa.
By Ultimately raising the Rainfall in the entire Southern Africa, through the managed and controlled filling and utilization of the Natural 30 000 - 60 000 square km of evaporation pans more regularly, will this not lower the extreme temperatures (day and night temperatures due to water absorbing much of the daytime heat and releasing it during the night) and drought patterns Southern Africa has experienced, and by all predictions are bound to worsen and could become more extreme?
In effect, creating a second Okavango Delta, but considerably bigger - large parts of Chobe.
A study of such a magnitude will need large amounts of research in multidisciplinary sciences, from Archaeology to Agriculture to Economics, and a much broader field of expertise - the biggest being Politics!
Could such a mammoth project not be but one small answer to a much bigger Climate Change challenge facing the Earth? (and ultimately send a bit of rain to my little piece of land in the Waterberg in the long dry winter months when we receive those dry West Winds - and fires become a serious hazard - simply by adding a bit of moisture from the vast pans Botswana are so blessed with!)
My mind has been going in circles as to the feasibility of such a mammoth, yet so cheap and easily implementable idea?
Any ideas? We agree that additional evaporation enhances energy transport from the surface to the atmosphere and intensifies the hydrological cycle and cloud formation, and that some of the most serious climate change issues such as:
The following is multiple choice question (with options) to answer.
as dryness increases in an environment, biodiversity | [
"increases",
"decreases",
"stays the same",
"begins"
] | B | as dryness increases in an environment , the available water in that environment will decrease |
OpenBookQA | OpenBookQA-555 | inorganic-chemistry, experimental-chemistry
Title: Proper disposal of calcium hydride/calcium hydroxide I had probably 2-3 grams of calcium hydride leftover in a schlenk flask from predrying a distillation of benzyl chloride. For the disposal, I diluted the flask contents in about 30mL isopropanol and then, over a water bath (flask open but under heavy stream of argon), added distilled water every few minutes until well after the bubbling had stopped, which I assumed was exothermic evolution of hydrogen gas. I also thought any leftover benzyl chloride would just make trace toluene, benzyl hydroxide, and calcium chloride.
I then figured the milky-white solution was okay to pour down the sink with lots of water running and removed about half of it in this manner, although I noticed a brief but strong smell from the vapors as I did so and stopped. I checked and noticed some sites place it into a basic waste container. Was it a mistake to pour down the sink? I thought limewater would be harmless with enough water. Were there any other errors in this process? I may have to repeat this in the future with calcium hydride again or phosphorous pentoxide (seen various methods on P$_2$O$_4$, but one mentioned sink disposal as well). The safest way to get rid of calcium hydride is to pour over ice. The water quenches the reagent itself, with the ice helping to control the exotherm (if you just add water, a lot of heat and gas is liberated, having a tendency to spray hot chemicals over the whole hood).
Once everythings quenched, it's helpful to add some hydrochloric acid before disposing of down the sink to prevent it clogging the drains.
Note that whilst clean calcium hydride is safe (once quenched) to be disposed of via the normal drainage, you must ensure any chemicals are washed off first (hexane works well), especially odorous things such as amines which you may have been drying with the calcium hydride.
The following is multiple choice question (with options) to answer.
Rubbing calcium on a streak plate | [
"describes a white mineral",
"leaves behind bits of white",
"tells a lot about calcium",
"breaks the calcium into chunks"
] | B | when a mineral is rubbed on a streak plate , some of the material breaks off and forms a powder |
OpenBookQA | OpenBookQA-556 | energy, acoustics, friction, resonance, perception
Title: What frequency is the scratching of finger nails on a blackboard? This is the frequency/intensity that sets my teeth on edge.
Does anybody know what frequency (roughly) it is? I am guessing it is near the top of normal human hearing, 20kHZ, but I'm not sure if that's why it affects me.
I am sure the same frequency is played on some of the music I listen to, but somehow, it does not make me wince.
There is a related question here, with no answer Scratching on a Blackboard, but I just want a frequency value. From http://www.livescience.com/16967-fingernails-chalkboard-painful.html:
Interestingly, the most painful frequencies were not the highest or lowest, but instead were those that were between 2,000 and 4,000 Hz. The human ear is most sensitive to sounds that fall in this frequency range, said Michael Oehler, professor of media and music management at the University of Cologne in Germany, who was one of the researchers in the study.
No one knows all of the reasons why that sound is so painful to listen to, but some theorize that we evolved ear canals to amplify human speech as much as possible, and that sounds like this happen to have large portions of their energy in that frequency band.
The following is multiple choice question (with options) to answer.
A smack on a wooden board can be heard a mile away | [
"because sound travels through oxygen",
"because of how sound works",
"because vibration can move",
"because sound vibrates through atmosphere"
] | D | sound can travel through air |
OpenBookQA | OpenBookQA-557 | botany, marine-biology, salt
Title: Mangroves and desalination of sea water I am not an expert but I guess that mangroves (or some other plants that thrive in sea water) perform some kind of desalination to extract fresh water from sea water.
Is this true? If yes, What biological mechanisms are used to remove salt from sea water?
I am interested in any research about biological desalination. This paper might be of interest to you: https://advances.sciencemag.org/content/6/8/eaax5253.
The researchers created a synthetic mangrove that actually performs desalination, using the principles of natural mangroves.
The introduction has a good overview of the main ways mangroves desalinate saline water, namely:
Physical blockage by suberin within cells walls
Selective permeability of cell membranes in root
Negative pressure caused by evaporation that acts as hydraulic pressure to cause take-up of water by roots
All these combine to turn the mangrove into a kind of natural RO (reverse osmosis) machine.
The following is multiple choice question (with options) to answer.
what does a cactus do with water | [
"spit it out",
"make it dirty",
"keep a cache",
"filter it"
] | C | a cactus stores water |
OpenBookQA | OpenBookQA-558 | species-identification, fruit
Title: What is this plant with hardened fruits on the beach in Mozambique? We saw these near the Barra and Tofinho beaches in the Inhambane province in Mozambique, in July. They were hard and leathery and dry to the touch, long past something resembling edible fruit.
Anybody have an idea what they might be? (just curious)
Edited: Here is some context around the tree. I will take a guess that it is Ficus racemosa which is found in that area. More info. If you have pictures of the rest of the tree that would be helpful.
The following is multiple choice question (with options) to answer.
Bananas, pineapples, and coconuts are from places that are | [
"warm",
"islands",
"wet",
"far away"
] | A | warm-weather organisms live in warm climates |
OpenBookQA | OpenBookQA-559 | species-identification, ornithology
Title: House sparrow or something else? These little flying fellows seemed to have made themselves a small nest in the crevices of the roof of my house (I live in Poland). I don't know if this makes a difference, but I do live near a small park.
I'm wondering if this is a house sparrow or something else.
On one of the photos I could swear these look like common sparrows, but on another (the one where the wings are apart) it seems like a different species. It also seemed larger than a sparrow, but is hard to tell due to the distance at which I've seen the birds and the photos were taken. One other notable feature was that they seemed very loud...
Any help? Based on your image I would rather identify it as an Eurasian Tree Sparrow. They are pretty similar to the House Sparrow, but have a distinct black spot below their eyes which is missing for the House Sparrows (image from the Wikipedia):
The following is multiple choice question (with options) to answer.
Some animals build a structure called a house for their own species to live in. This animal is a | [
"rodent",
"reptile",
"carnivore",
"primate"
] | D | some humans live in houses |
OpenBookQA | OpenBookQA-560 | evolution, zoology
Let's say the environmental challenge for two different kinds of carnivore (let's call them Bogs and Dats) is to catch Mophers. Both Bogs and Dats initially have the same medium-to-short muzzles. Some Bog individuals figure out that they can dig Mophers out of their burrows, and some Dat individuals figure out that they can catch Mophers at night when the Mophers leave their burrows. Both strategies are successful. Some Bogs happen to have longer muzzles than their cousins, and find it turns out that longer muzzles work synergistically with the digging strategy, allowing Bogs to stick their noses into the Mopher burrows to grab escaping Mophers. The resulting fitness advantage results in an increase of the long-muzzle trait in further generations of Bogs. Note that in this scenario it is the adaptive behavioral strategy that creates selective pressure that favors a particular genetic adaptation.
Dats on the other hand, because of their nocturnal hunting strategy, benefit from improved night vision; and long muzzles don't provide any fitness advantage to Dats because Dats don't dig Mophers from their burrows. As long as Bogs and Dats don't hybridize, they will most likely end up with long and short muzzles respectively.
The Waddington effect, also called “Genetic Assimilation”, is somewhat more direct:
An environmental stress causes a proportion of a population to develop one or more abnormal traits, by interfering with embryological development.
If there is a selective pressure in the environment that favors some subset of those traits, individuals whose genetic makeup makes them more likely to develop that subset of traits, those individuals are likely to produce more descendants than other members of the population.
If being “more likely to develop” that subset of traits results from a weakening of genetically determined development controls that would otherwise prevent development of that subset of traits, then the subset of traits can eventually become the normal phenotype.
The following is multiple choice question (with options) to answer.
Some animals get caught easily by other animals because they are slow while the predators are | [
"Nice",
"speedy",
"manipulative",
"crazy"
] | B | some predators move quickly to catch prey |
OpenBookQA | OpenBookQA-561 | star, galaxy
If you're on a farm, away from cities, in a place with reasonably low light pollution, and your eyes are good, and you've been sitting in perfect pitch black darkness for at least 30 minutes prior - when you look up you can reasonably expect to see a few thousand objects, mostly stars. Keep looking, and after a while you will distinguish one or two thousand more stars, very faint, that you could not see at first sight. Practice this steadily for a few years, and you'll add maybe another thousand; but you won't be able to see those all at once - only one at a time.
Now travel to the Cerro Tololo site in Chile, up in the mountaineous desert, zero light pollution, excellent transparency, and you'll multiply all those numbers by a factor of 2x ... 5x.
As you can see, the numbers are very flexible because there are so many factors involved. You can't just slap a 44k label on it and call it a day; that doesn't make any sense in reality. Astronomers know that the pure magnitude number doesn't mean much by itself, because it is just one factor among many.
In a place with very high light pollution (like where I live, in the middle of a large, dense, sprawling urban area in California), you'd be lucky if you can see a hundred stars at night.
Or, in a place with zero light pollution, shine a flashlight into someone's face, and you've temporarily blinded them. You've reduced the number of stars they could see by an order of magnitude for the next half hour (night vision gradually recovers, and it takes 30 minutes to fully recover, according to US military manuals and visual astronomers practice).
The following is multiple choice question (with options) to answer.
Seeing stars may become more difficult as | [
"stars are condensed in the sky",
"a greater amount of light is condensed in an area",
"floodlights are used at sea",
"spaceships begin to hover over earth"
] | B | as light pollution increases , seeing the stars will be harder |
OpenBookQA | OpenBookQA-562 | atmosphere, carbon-cycle
Title: For a tree over its entire existence, does it actually have a net negative effect on atmospheric CO2? A tree while alive converts CO2 + water -> carbohydrates + O2. However, once the tree dies, it decays, releasing CO2 back into the atmosphere. My question is, over an individual tree's overall existence, does a tree actually contribute to a reduction in atmospheric CO2?
I'm aware there's other pathways a tree could end up as a more long term carbon store (carbonaceous rocks), but mostly interested in if a tree were to die and fall in a forest, decay in 50-150 years, would it have contributed to a net reduction in CO2, or does a tree typically act as more of a temporary 100+ year store of CO2? A brief review of recent non-paywalled available literature indicates that such an effect likely exists but that it is difficult to quantify based on currently available data.
Some amount of carbon from trees can be sequestered in the soil for periods time significantly longer than the typical above-ground decomposition time of organic matter, potentially for millennia. This clearly lengthens the carbon cycle time, but it is not clear to me whether this represents carbon storage, as there does not seem to be a well established minimum cut-off time for this. The primary source for soil-sequestered carbon are tree roots, with leaf litter constituting a secondary source.
The following paper (preprint online) addresses the question in the specific context of agroforestry, i.e. cropland interspersed with trees. The paper notes multiple times that the processes involved in soil sequestration are not well understood and that quantitative measurements and estimates vary widely, as one would expect based on differences in climatic and soil condition. Note on units: A Mg corresponds to a metric ton.
Klaus Lorenz and Rattan Lala, "Soil organic carbon sequestration in agroforestry systems. A review." Agronomy for Sustainable Development, Vol. 34, No. 2, April 2014, pp. 443-454.
The following is multiple choice question (with options) to answer.
If a forest that is home to animals is cut down | [
"then the animals' homes are demolished",
"then the animals will just rebuild",
"then the animals will adapt",
"then the animals all die"
] | A | if a habitat is removed then that habitat is destroyed |
OpenBookQA | OpenBookQA-563 | lab-techniques, photosynthesis, chromatography
At the beginning, both cars (solutes) S1 and S2 are even with the solute front car (SF) because the race (chromatography) has just begun. However, over time, the SF car outpaces S1 and S2 because it is moving faster.
_______
/____/SF\___
|_,._____,._)
---`'-----`'--
_______
/____/S1\___
|_,._____,._)
---`'-----`'--
_______
/____/S2\___
|_,._____,._)
---`'-----`'--
And at the end, you get great separation:
_______
/____/SF\___
|_,._____,._)
---`'-----`'--
_______
/____/S1\___
|_,._____,._)
---`'-----`'--
_______
/____/S2\___
|_,._____,._)
---`'-----`'--
(Thanks to retrojunkies.com for the ASCII car)
The following is multiple choice question (with options) to answer.
The more that cars are driven, the more that | [
"daily temps will rise",
"birds will get sick",
"water will need purification",
"food will taste odd"
] | A | as the amount of polluting gasses in the atmoshere increases , the atmospheric temperature will increase |
OpenBookQA | OpenBookQA-564 | thermodynamics, climate-science
Title: Where does all the heat go during winter? I do not understand where actually the heat in our surroundings go during the winter season. Is it radiated out into space? I know it cannot coz global warming would not be a issue then. It might get absorbed but where? I tried figuring it myself but couldn't please help.
Where does all the heat go during winter?
There is less energy coming from the sun in the form of electromagnetic radiation impinging on the land during winter.
Depending on the latitude, in regions where there is winter , the difference is large.
The closer to the equator the smaller the effect of "winter".
So it is not where the energy goes, but why it does not fall , and this is explained to first order by the inclination and the distance to the sun during the orbit of the earth.
In general , a body in space radiates energy away the rate depending on various conditions, like green house gases, cloud cover, convection , albedo ...the numbers change . It is the continuous radiation from the sun that keeps replenishing the energy so that the earth does not freeze. During winter at high lattitutes , less energy comes and cold settles.
The following is multiple choice question (with options) to answer.
Bears hibernate in winter because | [
"to socialize more with other bears",
"the environment is colder and has less food",
"a fixed amount of time has passed",
"cubs are being born"
] | B | seasonal changes are made in response to changes in the environment |
OpenBookQA | OpenBookQA-565 | thermodynamics, photoelectric-effect, thermal-conductivity, absorption, solar-cells
Title: Possibility of combining photovoltaics and solar thermal energy In a private setting, photovoltaics and solar thermal energy are often harvested on the home's roof and roof area is limited. So, I thought about combining both, i.e. mounting solar collectors underneath solar cells. The rationale behind this is that the solar cells appear almost black and probably heat up considerably under irradiation. So if the collectors are in tight thermal contact to the cells, the water in the collectors might carry away the heat as usable energy, and possibly even increase the lifetime or efficiency of the cells due to the cooling effect (but this is rather engineering and not part of the question). So roof area is exploited twice (in two different wavelength windows). Moreover, if electric energy from the cells exceeds actual consumption and the battery's storage capacity, it might also be used for heating (albeit at a lower total efficiency, of course).
Can the amount of (infrared) radiation that gets absorbed (or possibly transmitted) by solar cells, and which is available as heat at the back side of the cells, be quantified by a rough calculation and either prove or disprove the benefit of such a concept? Does the almost black appearance of the solar cells fool one into thinking that they also absorb in the infrared, although they don't? Temperature of PV panels increases significantly during the day and their conversion efficiency decreases with increasing temperature. I had access to measurements of a PV plant and it showed that the total power production was about the same in August (middle of summer) and October (early fall). Although the days were shorter and there was less solar irradiance in October vs August, the air temperature was significantly lower making PV panels more efficient. For the outside temperature of 35 C, the PV panels can easily reach 70 C!
The following is multiple choice question (with options) to answer.
Which of these would absorb more sunlight | [
"A cave",
"A octopus",
"A bat",
"An elephant Ear"
] | D | as the size of a leaf increases , the amount of sunlight absorbed by that leaf will increase |
OpenBookQA | OpenBookQA-566 | performance, algorithm, c, memory-optimization, compression
"a",
"aaaaaaaaaaaaaa",
"\0",
"Powerلُلُصّبُلُلصّبُررً ॣ ॣh ॣ ॣ冗",
"When the sunlight strikes raindrops in the air, they act as a prism and form a rainbow. The rainbow is a division of white light into many beautiful colors. These take the shape of a long round arch, with its path high above, and its two ends apparently beyond the horizon. There is , according to legend, a boiling pot of gold at one end. People look, but no one ever finds it. When a man looks for something beyond his reach, his friends say he is looking for the pot of gold at the end of the rainbow. Throughout the centuries people have explained the rainbow in various ways. Some have accepted it as a miracle without physical explanation. To the Hebrews it was a token that there would be no more universal floods. The Greeks used to imagine that it was a sign from the gods to foretell war or heavy rain. The Norsemen considered the rainbow as a bridge over which the gods passed from earth to their home in the sky. Others have tried to explain the phenomenon physically. Aristotle thought that the rainbow was caused by reflection of the sun's rays by the rain. Since then physicists have found that it is not reflection, but refraction by the raindrops which causes the rainbows. Many complicated ideas about the rainbow have been formed. The difference in the rainbow depends considerably upon the size of the drops, and the width of the colored band increases as the size of the drops increases. The actual primary rainbow observed is said to be the effect of super-imposition of a number of bows. If the red of the second bow falls upon the green of the first, the result is to give a bow with an abnormally wide yellow band, since red and green light when mixed form yellow. This is a very common type of bow, one showing mainly red and yellow, with little or no green or "
}; /* A series of horrible strings that try and break the compression */
The following is multiple choice question (with options) to answer.
Rainbows need | [
"leprechauns and pots of gold",
"rain and dark skies",
"sun and some drizzle",
"sun and clear skies"
] | C | sunlight and rain can cause a rainbow |
OpenBookQA | OpenBookQA-567 | java, timer, benchmarking
Title: A simple Java class for implementing code stop watches - follow-up I have received a nice answer for this post. Now, it is my attempt for some improvement:
package net.coderodde.time;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
/**
* This class provides easy-to-use means for measuring elapsed time.
*
* @author Rodion "rodde" Efremov
* @version 1.6 (Feb 12, 2019)
*/
public final class StopWatch {
private boolean isMeasuring; // false by default.
private long startTimeMillis;
private long markTimeMillis;
private final List<Long> memory = new ArrayList<>();
/**
* Starts measuring time.
*/
public void start() {
setImpl(true);
}
/**
* Stops measuring time.
*/
public void stop() {
setImpl(false);
}
/**
* Resets the starting time to the current moment.
*/
public void reset() {
setImpl(true);
}
private void setImpl(boolean expectedStatus) {
if (expectedStatus) {
checkMeasuringStatusIsOff();
} else {
checkMeasuringStatusIsOn();
}
startTimeMillis = System.currentTimeMillis();
markTimeMillis = startTimeMillis;
isMeasuring = !isMeasuring;
memory.clear();
}
/**
* Marks current time for future calculation of lap times.
*/
public void mark() {
checkMeasuringStatusIsOn();
markTimeMillis = System.currentTimeMillis();
}
/**
* Returns the time elapsed from beginning of the current lap.
*
* @return the lap time.
*/
public long lap() {
checkMeasuringStatusIsOn();
long now = System.currentTimeMillis();
memory.add(now);
long saveMarkTimeMillis = markTimeMillis;
markTimeMillis = now;
return now - saveMarkTimeMillis;
}
The following is multiple choice question (with options) to answer.
A stopwatch is helpful | [
"when ascertaining what time it is",
"when tracking split times on runs",
"when setting an alarm clock",
"when ascertaining answers on a times table test"
] | B | a stopwatch is used to measure time |
OpenBookQA | OpenBookQA-568 | newtonian-gravity, mass, acceleration, earth, estimation
Title: Does Earth's Gravitational pull increase with time? Gravitational field depends on mass ($g = \frac{GM}{r^2}$) and every year many outside cosmic objects like asteroids or tiny object are hitting earth. So I think may be in a very microscopic amount the mass of Earth is increasing. But does it increase the Gravitational Pull or Gravity on Earth?
And also, does it result in decrease in height of organisms in each century? Because some older people say that people in their time or in ancient times were taller and more aged. I am just curious if it is the reason or not. Actually the opposite is true.
Quoted from Gizmodo - Did You Know That Earth Is Getting Lighter Every Day?:
Earth gains about 40,000 tonnes of dust every year,
the remnants of the formation of the solar system,
which are attracted by our gravity and become part
of the matter in our planet. Our planet is actually
made from all that starstuff.
Earth's core loses energy over time. It's like a giant
nuclear reactor that burns fuel. Less energy means less mass.
16 tonnes of that are gone every year. Not much.
And here's the big mass loss: about 95,000 tonnes of hydrogen
and 1,600 tones of helium escape Earth every year.
They are too light for gravity to keep them around,
so they get lost. Gone into space.
So, summing all these effects mentioned above,
you get a mass loss of 57,000 tonnes per year.
But this is still much too small to have a measurable effect on gravity
($g = GM/r^2$) even after millions of years,
because the mass of the earth is $M = 6\cdot 10^{24} \text{ kg}$
(i.e. 6,000,000,000,000,000,000,000 tonnes).
The following is multiple choice question (with options) to answer.
The pull of gravity on objects increase as what happens? | [
"the object gets further away",
"the object is pulled in circles",
"gravity is heavier on an object",
"the object is brought closer"
] | D | as distance from an object decreases , the the pull of gravity on that object increases |
OpenBookQA | OpenBookQA-569 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
A common problem involving waste in the excretory system is | [
"run for it",
"running on empty",
"running a fever",
"having the runs"
] | D | the excretory system removes waste from the body |
OpenBookQA | OpenBookQA-570 | newtonian-mechanics, estimation
Would the rock have created a seismic event of its own (if so, how large)?
Would the rock have created a crater? The energy of the rock at the time of hitting the earth is mgh.
No rock we know of is going to be able to survive this collision with out breaking into pieces.
Non the less it will be a big impact and depending on the geology of the location it hits a variety of reactions scenarios can happen.
If the soil is aggregate of silt and sand and gravel, it would part into several shear rupture sections which look like slices of shell pattern surfaces starting from the bottom surface of the rock and turning up exiting the earth surface a few hundred yards outside of the impact zone and probably even eject some material out like a bomb crater. This scenario will have shakes that could be recorded miles away.
The calculation of how much of the momentum of rock will be shared with the shear material and accelerating them will be involved but not impossible.
If the geology of the impact area is of very low bearing like mostly silt and loose clays, the rock my lose most of its kinetic energy by just sinking into the dirt mostly with a giant humph with a cloud of dust rising.
If the geology is hard or rocky with the 'optimal' amount of mass and resilience it could create a substantial earthquake by resonating with the impact.
The following is multiple choice question (with options) to answer.
some level of crushing and pressure would be needed for sedimentary rock formation | [
"this is accurate",
"maybe true",
"this is untrue",
"all of these"
] | A | sedimentary rocks are formed from sediment compacting together |
OpenBookQA | OpenBookQA-571 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
which of these will lead to a larger population in a given habitat? | [
"all of these",
"severe famine and starvation",
"severe drought and dryness",
"a bountiful assortment of meals"
] | D | as the number of sources of food increase in an environment , the population of the organisms will increase in that environment |
OpenBookQA | OpenBookQA-572 | atmosphere, wind, geography, troposphere, stratosphere
Title: Other than the South Pole where is the windless place on Earth? For this other question "Would this chambered cylinder be possible", preferably near the equator where is a calmest place from the troposphere to the stratosphere where is the windless place one Earth most of the year? Not just the south pole, but 'Ridge A' and many other parts of the high Antarctic Plateau, at or about 4000 metres altitude, are generally recognized as being the least windy. Otherwise, there are a many parts of the high pressure belts at about +/- 30 degrees which have little wind for most of the year. These tend to be very dry deserts where occasional winds have momentum from other regions. On a local scale there are some deep valleys in tropical rain forests. Once you get below the canopy turbulence level they seldom receive winds of any significance - just the lightest breeze from impeded convection. However, records are hard to find because anemometers in such locations are not really representative of anything.
There is an instagram which claims that Fern tree bus stop, in Hobart, Tasmania, is the 'calmest place on Earth'.
But my experience of Hobart is that icy winds in winter can be far from calm.
These things are relative. Compared to the 2100 km/hour winds of Neptune, everywhere on our planet is as close to windless as makes no difference.
The following is multiple choice question (with options) to answer.
Where is December warmest? | [
"Nebraska",
"Canada",
"Papua New Guinea",
"Israel"
] | C | December is during the summer in the southern hemisphere |
OpenBookQA | OpenBookQA-573 | cellular-respiration
Title: Do cold blooded animals generate any heat? In explaining energy and work to an 8 year-old I said that all conversion of energy generates heat as a by-product. For example, cars generate heat in their engines and running generates heat in our bodies. Then the 8 year-old said, except for cold-blooded animals.
So my question is, do cold-blooded animals generate any heat in their conversion of stored energy (food, fat, etc) into motion? If they generate heat, why are they cold-blooded? They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies.
An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual purpose, but to function as a furnace. "Warm-blooded" and "cold-blooded" is somewhat a misnomer. The correct way to think of it is...
Endotherm or ectotherm. Does the heat primarily come from within (endo) or from the surroundings (ecto). Endothermic animals include mammals. Most of their body heat is generated by their own metabolisms. Ectothermic animals include reptiles and insects. They absorb most of their body heat from the surroundings. This is not the same as saying they let their body temperature fluctuate with their surroundings, some avoid this by moving around to accomodate themselves.
Homeotherm or poikilotherm. Homeotherms want to maintain homeostasis for their body temperatures. They don't want it to change. Poikilotherms do not exhibit this behaviour, instead their body temperatures vary greatly with the environment.
We can have endotherm poikilotherms, such as squirrels, who let their body temperature drop while hibernating. Endotherm homeotherms, such as humans, where temperature is constant by means of complex thermoregulation. Ectotherm homeotherms, such as snakes (moving into shadow or into the sun to regulate temperature), and ectotherm poikilotherms, such as maggots.
The following is multiple choice question (with options) to answer.
whether hot or cold blooded, to survive all animals are required to | [
"store radiant heat",
"wash with water",
"bath in sunshine",
"fight to survive"
] | A | an animal usually requires a warm body temperature for survival |
OpenBookQA | OpenBookQA-574 | visible-light, sun, weather
Title: Why are clouds lighter than the sky during the day but darker at night This is probably a very basic question but I couldn't find a good answer to it, most search results are about rain clouds or clouds appearing red at night (something I've never seen except for during sunset but apparently it's common in bigger cities).
Basically what I'm wondering is why clouds during the day appear lighter than the sky (white vs light blue) while clouds at night and during the evening appear darker than the sky (see image).
Image quality is low because I took it with my phone through my window.
I guess the clouds could be blocking the light and therefore appear darker but in that case, shouldn't the same thing be happening during the day? There could be quite a few things going on.
Off the bat there's no incoming light for them to scatter: during the day, clouds are white because the water droplets are big enough for all visible light to cause Mie scattering, but if you don't have much light falling on them, you can't observe the scattering and you can't observe light passing through either.
Then you could consider the fact that in some places, it rains more in the evening/night than during the day (if you have hotter surface temperatures during the afternoon, you see cloud formation and precipitation during the late evening, and with the lower temperatures in the night, the air is more likely to become saturated, see Dew Point), and clouds which precede rain are thicker and denser. They don't allow much light pass through.
And lastly, there's less ambient light which they can reflect back towards you.
The following is multiple choice question (with options) to answer.
There is more rain when the sky is | [
"gray",
"red",
"blue",
"white"
] | A | if weather is stormy then there is a greater chance of rain |
OpenBookQA | OpenBookQA-575 | melting-point, decomposition
Salts with stronger acid and base components are more difficult to decompose, because more energy is required to reverse the acid-base combination. Magnesium sulfate has a higher decomposition temperature than zinc sulfate because magnesium oxide is a stronger base than zinc oxide. Similarly, magnesium sulfate requires a much higher temperature to decompose than magnesium carbonate; the latter decomposition requires evolving weakly acidic $\ce{CO2}$ whereas the former would have to evolve strongly acidic $\ce{SO3}$ or couple the acid-base separation with the thermal decomposition of $\ce{SO3}$ to $\ce{SO2 + (1/2) O2}$. Sometimes redox reactions can facilitate decomposition if they convert stronger acids and bases to weaker ones, such as ammonium nitrate being decomposed to water and nitrous oxide rather than ammonia and nitric acid.
The following is multiple choice question (with options) to answer.
Decomposition is important for | [
"water",
"medicine",
"sunlight",
"food"
] | D | decomposition is when a decomposer breaks down dead organisms |
OpenBookQA | OpenBookQA-576 | meteorology, mesoscale-meteorology
In a sense, the fact pressure at one elevation induces changes\motion in another elevation maybe shouldn't seem any less weird than the fact that a low-level low pressure system can affect the wind and weather hundreds of miles away from it horizontally. This isn't spooky action at a distance, this is a continuous fluid where changes to one part of it causes impacts on another part.
The following is multiple choice question (with options) to answer.
How is a place of lower elevation affected by flooding when compared to a higher location? | [
"It is more affected by the flood",
"It is impossible to flood a lower elevation location",
"It is more resistant than a higher place",
"The lower area is already flooded"
] | A | as elevation of a place decreases , how much a flood will affect that place will increases |
OpenBookQA | OpenBookQA-577 | c#, random, bitwise
this.seed = internalSeed;
// 2D gradients
gradient2Dx = new double[256];
gradient2Dy = new double[256];
// fill x and y arrays
for (int i = 0; i < 128; i++)
{
gradient2Dx[i + 000] = (i & 15) / 7.5 - 1;
gradient2Dx[i + 128] = (i & 15) / 7.5 - 1;
double a = Math.Abs(gradient2Dx[i]);
gradient2Dy[i + 000] = 1 - a;
gradient2Dy[i + 128] = a - 1;
}
// shuffle arrays
for (uint i = 255; i >= 1; i--)
{
uint j = GenUInt(i + 1);
double a = gradient2Dx[i];
double b = gradient2Dy[i];
gradient2Dx[i] = gradient2Dx[j];
gradient2Dy[i] = gradient2Dy[j];
gradient2Dx[j] = a;
gradient2Dy[j] = b;
}
// 3D gradients
gradient3Dx = new double[256];
gradient3Dy = new double[256];
gradient3Dz = new double[256];
// fill x, y and z arrays
for (int j = 0; j < 16; j++)
{
for (int i = 0; i < 16; i++)
{
gradient3Dx[i + (j << 4)] = gradient3DxData[i];
gradient3Dy[i + (j << 4)] = gradient3DyData[i];
gradient3Dz[i + (j << 4)] = gradient3DzData[i];
}
}
// shuffle arrays
for (uint i = 255; i >= 1; i--)
{
uint j = GenUInt(i + 1);
double a = gradient3Dx[i];
double b = gradient3Dy[i];
double c = gradient3Dz[i];
The following is multiple choice question (with options) to answer.
Seeds can be found inside an object often seen on | [
"Saturday",
"Valentine's Day",
"April Fool's Day",
"Halloween"
] | D | a pumpkin contains seeds |
OpenBookQA | OpenBookQA-578 | formal-grammars
Title: Useless production Kindly consider the following productions. How can I identify a useless production?
S->aS|A|C
A->a
B->aa
C->aCb
Somebody please guide me.
Zulfi. Starting from $S$ it is impossible to generate a sentential form that contains the nonterminal $B$.
This is easy to see since:
$S$ only has productions whose body contain $S$ itself, $A$ or $C$.
$A$ has no nonterminals in the body of its productions.
$C$ has only $C$ itself in the body of its productions.
This means that the production $B \to aa$ is useless.
The following is multiple choice question (with options) to answer.
A producer makes its own what? | [
"air",
"grass",
"body",
"sustenance"
] | D | a producer produces its own food |
OpenBookQA | OpenBookQA-579 | waves, atmospheric-science, turbulence
The clouds form if the rising air reaches the lifted condensation level before the updrafts are stopped by an inversion or stable layer. The air is (relatively) clear above the downdrafts. If the convection rolls were perfectly circular, the cloud row spacing would be twice the height of the inversion/stable layer.
Mathematically, there are many wavelength solutions to convection, but the wavelength that dominates is the fastest growing one. In the Boussinesq approximation, which is reasonably valid here, this turns out to have a wavelength of $2\sqrt{2}\sim 3$ times the height of the convecting layer, i.e. slightly flattened. (See, for example, Eq. 21 of Kuettner (1971) "Cloud bands in the earth's atmosphere: Observations and Theory".)
For typical cumulus cloud heights of $\sim 2$ km, we expect typical spacings of about $6$ km.
Wave, lee, or mountain clouds are lines of clouds downwind of an obstacle (such as a mountain range). The lines are parallel to the wind direction. These are buoyancy waves where wind pushes denser air over an obstacle (e.g. a mountain range) and it ends up above less dense air on the other side. This dense air starts to fall but it overshoots into even higher density air at lower altitude, which forces it back up, and the air ends up bouncing up and down until the oscillations die out. If the vertical temperature profile of the air then is known, it is possible to estimate the vertical buoyancy angular frequency
$$N=\sqrt{\frac{g}{\theta}\frac{d\theta}{dz}}$$
The following is multiple choice question (with options) to answer.
Clouds are made up of moisture particles that are held in the sky until | [
"weight works against it",
"the storm starts to approach",
"the weather starts to change",
"winter arrives sooner than later"
] | A | clouds produce rain |
OpenBookQA | OpenBookQA-580 | zoology, behaviour, mammals, rodents
Title: Why do Guinea Pigs chirp / sing? Ok, so this appears to be quite a mystery. Me and my girlfriend have 2 Guinea Pigs, 1 male and 1 female.
My girlfriend once picked up the female one and took her outside into our garden. The Guinea got scared for some unknown reason and jumped out of my girlfriend's arms and fell down hard.. That night, the female Guinea woke us up with some very strange sounds. She sounded like a chirping bird.
Since then, she sometimes repeats these sounds (most often at night, but not always). Mostly, we are puzzled as to why as there is often no apparent reason for her sounds. Also, when she makes the sounds, she appears to be in a trance-like state, making no movements at all.
Looking for the answer online I found many discussions on the subject like this one or this one. Mostly, the sounds (and the often mentioned trance like behavior) appear to be interpreted as either (1) alarm sounds, (2) loneliness sounds or (3) happiness sounds.
There are also recordings of it one Youtube, like this one.
What I was wondering:
Does anybody know about some actual research that has been committed on this subject? If so, what were the results?
I'm just so very curious to find out! I found this question very interesting so I did some research. Here's a brief summary of what I've found:
Researchers have found that there are 11 different call types. Some of these include a "sharp alarm cry", "sociable clucking", chutter, whining, purring etc. Using body position and behaviour, researchers attempted to associate these vocalizations with behaviour. Some vocalizations had no apparent associated action including what researchers designated the "chirrup" ( I think this is similar to what your guinea pig might have emitted.)
For more information you can read the results section of this paper by Berryman. You can find a full description of each of the 11 calls and their assumed cause or purpose. Some involve social interaction, reproduction, and distress. Much of the research regarding Guinea pig vocalization involves communication and response between mothers and pups.
In short, it seems as though this chirping behaviour your Guinea pig is exhibiting is normal, but not of any known cause.
The following is multiple choice question (with options) to answer.
what is a mammal's parenting behavior? | [
"they give nutrition to their young",
"they lack care for their young",
"mammals eat their young",
"mammals have zero offspring"
] | A | a mammal usually nurses its offspring |
OpenBookQA | OpenBookQA-581 | paleoclimatology
Has trees, i.e., long-lived woody plants that are capable of growing at least ten meters tall and that grow both upward by extending new branches and outward by widening of the trunk. Amongst other things, this rules out times before ~380 million years ago, which was when the first trees formed.
Has sufficient trees so as to constitute a forest, which I'll define as a largish area where trees grow sufficiently dense so as to form a more or less closed canopy. This distinguishes forests from areas with only a few trees such as savannas and krummholz.
Has very harsh winters, with at least one month where the average temperature is well below freezing, and temperatures of -40° C are not rare. This distinguishes boreal forests from cold oceanic forests such as the Magellanic subpolar forests in southern Chile and Argentina.
Has mild summers, with only a few months where the average temperature exceeds 10° C. This distinguishes boreal forests from hemiboreal and temperate forests. Note that some scientists do not make this distinction, classifying Köppen climate zone Dfb as boreal.
Is extensive. This distinguishes large boreal forests from high altitude subalpine forests that would locally pass the above tests. Subalpine forests can occur at any latitude, including Australia's Snow Mountains, New Zealand's Southern Alps, and parts of the Andes. This is not a clear-cut boundary. As a climate cools, subalpine forests may spread to the valleys between mountains and then spread out beyond the mountains. At some point, such montane forests becomes boreal forests.
The following is multiple choice question (with options) to answer.
There are very few species of plants and animals in places like the North Pole because the temperatures are always very | [
"muggy",
"low",
"high",
"boring"
] | B | cold environments contain few organisms |
OpenBookQA | OpenBookQA-582 | homework-and-exercises, pressure
Title: Why is it difficult to cook food on mountains? Why is it difficult to cook food on mountains?
Is it because on increasing pressure boiling point of substance increase and on mountains there is less pressure so less boiling point. Then shouldn't it be easier to cook food on mountain.
I know that as we go to higher altitude there is less oxygen so it becomes difficult to cook. My teacher gave this question when she was teaching about boiling point and "How pressure effect boiling point?" so the reasoning should be of something about pressure. Why do we boil water to cook food? It's not actually because there's anything magic about the boiling of water, or that the physical process of boiling in particular does anything. Usually it's because we want a constant-temperature heat bath. Say you are boiling vegetables. You boil water, and you know that water is at 100 degrees. Water actually cannot get any hotter than this--it stays at that temperature or it becomes steam and leaves the pot. Then you put the vegetables into the boiling water, and therefore you know that they are in a 100 degree environment. Then, you know you need to leave them in there for however long--let's say five minutes.
Suppose, though, you were at high altitudes and water boiled at 95 degrees. Well, now when you put your vegetables into boiling water, they are only in a 95 degree environment, so the cooking time has changed. Your recipe no longer works correctly, and you will have to boil the food for longer.
Or maybe not, actually. The other possibility is that you are putting food in an oven, say something that's supposed to be 200 degrees. In this case, the water that's probably in the thing you're baking actually keeps the food cooler for longer. It reaches 100 degrees and will stay there until it boils off. However, if it boils off at 95 degrees, then again your cooking parameters will have changed. Since the water boils off faster, your dish spends more time at higher temperatures and can burn.
The following is multiple choice question (with options) to answer.
The family cooked most of their food using a stove and | [
"electricity",
"luck",
"ice",
"magic"
] | A | electrical devices convert electricity into other forms of energy |
OpenBookQA | OpenBookQA-583 | sexual-reproduction
So when it's not maintained -- when there's no selection pressure on two populations -- inevitably there will be genetic drift that will randomly disrupt this fine-tuned system. If a population of, say, voles is isolated on an island, they will continue to have pressure to be able to interbreed with other voles on the island, but if they can't interbreed with those on the mainland there won't be any consequences, and so over long enough time they'll drift and lose that ability -- just as many apes, not suffering any consequences from not synthesizing vitamin C, gradually lost that ability from random drift.
There's another side to it. Two populations in the same location may be positively selected to not be able to interbreed. Think about two groups of finches, one with small fine beaks that eat tiny seeds deep inside pine cones, and one with heavy beaks that crush and eat thick-shelled nuts. They each do fine, but they can interbreed and produce offspring that have intermediate beaks -- too thick to reach the fine seeds that one parent eats, but too delicate to crush the nuts that the other parent eats. Those intermediate offspring will die off, and both parents will have wasted their resources raising them. Both parents would be better off not breeding with each other, but only breeding with their own kind to produce specialized and efficient offspring. There is now selection pressure on the birds to recognize their own kind (perhaps through songs or mating displays) and ultimately to be inter-sterile, so they never waste resources on the un-fit offspring. There's a gradation of separation over time, in which the different populations become more and more distinct. Eventually, at some arbitrary point, humans start calling them "species", but that's just us, not biology.
"Species" is an important concept, but it's not special in evolution; speciation is just one aspect of natural selection, there's nothing magical about it.
The following is multiple choice question (with options) to answer.
Many plant species can only reproduce if the environment includes | [
"fungi",
"ants",
"bees",
"spiders"
] | C | A bee is a pollinating animal |
OpenBookQA | OpenBookQA-584 | thermodynamics, evaporation, gas, liquid-state
On the water surface, knowing the temperature, we can estimate the vapor pressure and vapor mixture fraction. Then there will be an diffusion process for the water vapor to move out and for the ambient air to move in. Because the water surface doesn't allow the air to further move, a circulation forms. When the water vapor moves out, the water vapor pressure drops, so more liquid water evaporates to fill up the loss of water vapor. The evaporation associates latent heat so water surface area temperature drops (you may see dew on the bowl wall). Then a heat transfer process starts which may initiate water circulation as well.
As this is complex, doing test might be a quick way to get the K value if you assume it is a constant, which is questionable.
The following is multiple choice question (with options) to answer.
Water vapor cooling | [
"will thoroughly evaporate into the air",
"will quickly become ice",
"becomes steam in the atmosphere",
"becomes droplets of h2o on a boiling pot's lid"
] | D | water vapor cooling causes that water vapor to condense |
OpenBookQA | OpenBookQA-585 | 5. Hello, James!
Another approach . . .
12 Students are in a class.
Five can go to room A, Four to room B, and Three to room C.
How many ways can this happen?
Assign 5 students to room A.
. . There are: . $_{12}C_5 \:=\:\frac{12!}{5!7!} \:=\:792$ ways.
From the remaining 7 students, assign 4 students to room B.
. . There are: . $_7C_4 \:=\:\frac{7!}{4!3!} \:=\:35$ ways.
From the remaining 3 students, assign 3 students to room C.
. . Of course, there is: . $_3C_3 \:=\:1$ way.
Therefore, there are: . $792 \times 35 \times 1 \:=\:27,\!720$ ways.
The following is multiple choice question (with options) to answer.
if a student locates their pen on the table across the room, which of these happened? | [
"there was light from pen to cornea",
"the pen failed to reflect any light",
"none of these",
"the person has psychic powers"
] | A | if an object reflects light toward the eye then that object can be seen |
OpenBookQA | OpenBookQA-586 | mass, velocity, weight
Wind stroke and area of existing large flying birds (and Haast Eagles) are approximately optimum for the load.
Modern materials will allow flying-related swept area per mass to be as good as or better than nature has achieved in these large birds.
This violates the usual cube-squared law that usually requires scaled-up versions of a given creature to be substantially more sturdy and thick-boned, and scaled-down versions to be much more "delicate". This is because the volume and (more or less) the mass changes with dimension cubed but areas such as bone cross-section to change with dimension squared. So a linearly scaled-up ant of elephant size would break apart under its own weight and muscle forces and a linearly scaled-down elephant of any size would be vastly too massive for its energy and power capabilities.
Feather size scales at most linearly with dimension squared - ie a Haast Eagle scaled up to man mass size would have feathers in the same proportion to size as on the original, or smaller.
Wing design will be "something like" the best examples available in nature. While many people probably thing that they could greatly improve on current designs, the experience base is very limited compared to the competition and so far design successes are few.
The following is multiple choice question (with options) to answer.
Thick feathers come in handy for birds | [
"that live in warm climates",
"who like a fluffier look",
"that live in frigid climates",
"who suffer from male patterned baldness"
] | C | thick feathers can be used for keeping warm |
OpenBookQA | OpenBookQA-587 | safety, equipment
Finally, make sure someone doesn't get the idea that the hood will stop all fumes and try to do a perchloric acid experiment using that hood--that will go badly.
Now, all this being said...
What you really need isn't to make this safe, what you need is to convince administration that you're doing things safely. This may have nothing at all to do with whether things are actually safe or not.
At my old school (where I was briefly president of the local ACS chapter), I could have put an experiment into a fume hood with no filter, not plugged the thing in, and gotten an okay from the administrators because they believed that fume hood = safe and no fume hood = unsafe no matter what else was going on.
I say this not to encourage you to try to trick your way out of this, but to point out that, unless your administration is scientific (i.e. actually understands science), then it's fairly likely you're going to have to jump through a few silly hoops in order to satisfy them.
Best of luck!
The following is multiple choice question (with options) to answer.
What is safest to breathe around? | [
"coal plant",
"Union Carbide plant",
"windmill",
"automobile"
] | C | a windmill does not create pollution |
OpenBookQA | OpenBookQA-588 | oceanography, sea-level, tides
Title: Why do high tides vary month to month? I've noticed that some ‘highest‘ high tides in one month are bigger than the highest high-tide of previous months. Why is this so? The dynamics of the tides are quite complex. The main idea is that gravity from the Moon and the Sun affect water (and everything else) on Earth. The issue is that there are several motions that alter the distance between the 3 systems and those motions cause interactions between the different frequencies involved. The Equilibrium Theory of Tides separates the different effects into a set of constituents by conducting a harmonic analysis. The relevant periods are:
the lunar day (period of lunar rotation), 24.84 mean solar hours.
the sidereal month (period of lunar declination), 27.32 mean solar days.
the tropical year (period of solar declination), 365.24 mean solar days.
the period of the lunar perigee, 8.85 years (1 year = 365.2421988 days).
the period of the lunar node, 18.61 years.
the period of the solar perihelion, 20940 years.
The explanation of each constituent can be rather complex (some examples in this other answer). The different amplitudes in a day and the spring-neap cycle are related to the combination of the main lunar and solar effects.
The differences in high/low tide from month to month are related to the next two main frequencies of oscillation. Mainly, the variations in Earth-Sun distance associated occurring in a period of tropical year. The lunar distance also contributes to these differences, but its cycle is much longer (~9 years). Also, the spring-neap cycle (with a frequency of half a lunar month ~13.5 days) will occur at different times of the month and can lead to differences in tidal amplitude if you compare the tides measured the same day of consecutive months.
(Source www.niwa.co.nz)
The following is multiple choice question (with options) to answer.
Bill missed high tide, so he had to wait until when to see it again | [
"tomorrow",
"next month",
"next year",
"never"
] | A | the moon rising occurs once per day |
OpenBookQA | OpenBookQA-589 | entomology, ant
Title: In an ant (or bee) colony, what is the very approximate ratio of new breeders to workers? For example, out of every 1000 eggs laid, X mature into drones and/or virgin queens. That seems impossibly precise but it illustrates the kind of number I want well. I'll accept answers for any species and any number of species, even one, with any amount of precision or lack thereof, because right now I can't even feel confident saying that there are more workers or more breeders, though I obviously suspect more workers.
I would also be ecstatic to have any live count just before the nuptial flight, i.e. for this colony in this study there were X workers, Y drones, and Z virgin queens just before the nuptial flight, or X workers and (Y+Z) breeders, or X% of the colony was breeders, or for this species on average X% are breeders just before the nuptial flight.
Anything. Any one thing and I can accept it as an answer.
I can find any number of studies that talk about the sex ratio between drones and virgin queens, so I know someone is counting. Maybe I'm not reading closely enough, but they always seem to slip away from giving all the numbers I need to figure this out for myself. So.
This answer is specific to the western honeybee, Apis mellifera, as there are massive amounts of data on them; more, possibly, than any other insect species. There has certainly been more data collected about them than any other hymenopteran.
At around the time of the nuptial flight, there may be as many as 60,000 workers in the hive, though likely number is more like 15,000 - 20,000. There will be either one (virgin) or two (one mated, one virgin) queens (the old queen will stay with the hive, if she is alive). There may be as many as 400 drones from the original colony (though usually the number is less, around 150 is typical; 10 - 50 of them will actually mate with the queen), and an equal number may join in the flight drawn from other colonies, especially in commercial beekeeping operations. Somewhere between 1000 - 6000 workers will take part in the nuptial flight with the virgin queen and the drones.
The following is multiple choice question (with options) to answer.
The bee provided a valuable service to the | [
"house.",
"rock",
"water",
"rose"
] | D | An insect is a pollinating animal |
OpenBookQA | OpenBookQA-590 | hygiene, food-chemistry
Dishes and utensils are only susceptible to bacterial growth if there's traces of food on them. Washing is meant to remove traces of food and oil so bacteria can't multiple on them. The conditions must be right for bacteria to multiple. If traces of food were to be completely dry and hardened on a dish and someone ate off it, the likelihood of any bacteria present on it is close to nil. They need moisture to grow. If dishes had no oily food on them, washing and rinsing with very warm water would be sufficient. I've seen people from other cultures wash dishes with traces of food that are soluble in water. They come out perfectly clean. (As an aside, using a tea towel can often spread bacteria when they're not used properly.) Towels top kitchen contamination hazards list
Bacteria can't multiple in oil. For example, ordinary cooking oil doesn't need to be refrigerated although it can go rancid. A cast iron frying pan is properly meant for frying foods only. No watery sauces should be cooked in them. Even "scraping it clean" shouldn't be done with a sharp metal object as it can remove some of the polymerized hardened oil layer.
I have several cast iron pans that I don't wash. I wipe them out after each use, then I add a little oil nd roughly a teaspoon of salt. With a paper towel, I rub at any bits of stuck on food. If done within a few hours of being used, it effectively removes any food traces, leaving a smooth surface. I usually rinse off the salt in warm water, dry it and then apply a very thin film of oil. I've been cooking in cast iron pans for decades and have never gotten sick or had mild food poisoning (what many people call a 'stomach flu').
Cast iron pans with a layer of proper seasoning and treated like this will definitely not cause sickness. It can't support bacterial growth and as @jeanquilt mentions, the pan gets very hot - enough to blister your skin if you touch them with a bare hand.
The following is multiple choice question (with options) to answer.
When washing laundry, dishes, or taking a bath, it is vital to have | [
"seven pails for water",
"a hot water heater in the city",
"a large brush for scrubbing",
"water which is warmed to acceptable temperatures"
] | D | a shower is a source of hot water for washing |
OpenBookQA | OpenBookQA-591 | paleontology, fossils, desert
Title: Why are many fossils found in deserts? Why are deserts famous for fossils? Is it a coincidence? Some examples:
Giant Catfish Fossil Found in Egyptian Desert
Chile's stunning fossil whale graveyard explained
Giant Dinosaur Fossil Found in Sahara Desert I would contend that the fact that the location is a desert has little to nothing to do in most cases to the existence of fossils at the location. Most of the fossils in the location, at least the ones that make most headlines like major dinosaur deposits, were left there millions of years ago. The fact that a location today is a desert has no indication of what the climate, or even where on the globe that location was 50 or 100 million years ago.
Do not forget about plate tectonics and climate change. One can go to places like the Judith Basin in Montana, a relatively harsh area of North American Bad Lands, desert or near desert like conditions with cold winters and find fields of fossils from animals that are believed to have lived in tropic marshes of in oceans, because at the time those animals lived, what is now Montana was not inland, and was not at a Northern location. Millions of years ago it was an undersea plate, thus it has layers of limestone made from ancient single cell sea creatures and sometimes larger objects that were entrapped and preserved as larger fossils. At other times, those plates rose from the sea floor and homed some of the large creatures, like T-Rex that lived, thrived and sometimes survive as fossils.
Later, that plate move and ended up inland, in what is not North America. Glaciers, wind, and water may have stripped off many layers of deposits and left exposed or close to exposed the layers of interest to fossil hunters. Desert regions tend to be subjected to this type of erosion and exposure making such finds easier. If those same fossils were in and area such as a rich planes area with plentiful plant growth and never subjected to glacial scouring, they could be, and may very well be, right below your feet but under many layers of soil and decaying vegetation, river sediment and other deposits rendering them out of sight and out of reach.
The following is multiple choice question (with options) to answer.
A desert environment is | [
"frigid",
"parched",
"rainy",
"tropical"
] | B | a desert environment is dry |
OpenBookQA | OpenBookQA-592 | quantum-mechanics, homework-and-exercises, wavefunction, schroedinger-equation, scattering
What this is saying is the that phase-shift increases without bound (or moving seamlessly through $90^o$ and $-90^o$. I would expect the phase shift to decrease with increasing energy, eventually settling at zero. I'm pretty sure I've messed up something. Could you help me out? I figured it out. The problem was that I was simply adding the two phase shifts, ignoring the periodicity in the tangent and arctangent functions. In order to get the proper result/plot, one can resort to the addition formula for tangents
$$\delta=\delta_1+\delta_2=\arctan \left(\frac{\frac{\epsilon}{2}\tan(2k'a)-\tan(2ka)}{1+\frac{\epsilon}{2}\tan(2k'a)\tan(2ka)}\right)$$
The following is multiple choice question (with options) to answer.
Phase changing occurs when | [
"water is poured into a glass",
"cake is left to cool on the counter",
"jello mix is refrigerated",
"turkey is sliced into pieces"
] | C | a phase change is when matter changes from one state into another state |
OpenBookQA | OpenBookQA-593 | human-anatomy
Taken from here such people would be able to dislocate then get their hands in front and relocate.
The body can be trained to be quite flexible through training like gymnastics etc...
The following is multiple choice question (with options) to answer.
A ramp can move a person to what level? | [
"a pulley",
"handicapped",
"a higher one",
"darker level"
] | C | an inclined plane is used for raising objects |
OpenBookQA | OpenBookQA-594 | newtonian-mechanics
I should add that the above is simply what I, as a physicist with a fairly long experience, suspect is what is going on. It is not something I have read about and I am sure there is somewhere a more thorough discussion. So I hope I am right; I think I have a good argument. As I have described it above, I have in mind mainly the last part of the process where the wood only moves a little relative to the metal. In the earlier part, when the wood moves through a larger distance, it is inertia that is the main consideration, just like in the party trick where you abruptly whisk away a table cloth and the dishes on the table stay where there are. The more abrupt the better.
Added remark
It occurred to me that there is another thing worth mentioning here, that makes this method preferable to resting the axe head on something, or supporting the handle on a work top and hitting the head. It is that by hitting the end of the handle, with the head just hanging, you are going to deliver the force more accurately at the join, because it travels along the handle in exactly the direction you want. If instead you strike the head then there is a danger it will be knocked slightly obliquely, introducing a random tilt with each blow, which is liable to deform the wood and thus loosen the fit.
The following is multiple choice question (with options) to answer.
Altering the physical structure of an object destructively might involve | [
"building on top of the item",
"getting it broken to pieces",
"none of these",
"producing a better quality version"
] | B | breaking down an object changes that object 's shape and mass |
OpenBookQA | OpenBookQA-595 | astronomy, everyday-life, popular-science, climate-science
It is for much the same reason that Winter is colder than Autumn, even though they have the same amount of daylight hours.
The following is multiple choice question (with options) to answer.
An area where snow falls more of the year is often | [
"rainy",
"windy",
"higher",
"forested"
] | C | snow falls during the winter in some environments |
OpenBookQA | OpenBookQA-596 | experimental-physics, water, fluid-statics
Title: Determine water level difference in two ponds I live near two ponds whose water levels appear to differ by a few feet. The ground is hard clay, so I don't think there's any underground water exchange between the ponds. The ponds are separated by about 30 feet of a bumpy terrain, with the bumps reaching a few feet above the "higher" water level. What is the cleverest way to determine the difference in water levels between these ponds? What comes to mind is to stick two poles (several feet high) at the water line in each pond, stretch a string between them, level the string with a bubble level and measure the distances between the string and the water level on each pole. Any other ideas? Fill a garden hose with water. Hold both ends closed, and walk to the "higher" pond. Have someone helping you hold the end of the hose under water.
Now walk to the other pond (still holding the end of the hose shut). Hold the hose near the surface of the pond - you should feel water pressing against your finger. Make a very small opening and observe the water coming out.
Now raise the hose slowly. At the point where the water stops flowing, the end of your hose is at the level of the higher pond.
Measuring the height difference is now trivial.
Incidentally - you mentioned that the ground between the two ponds was "bumpy". This raises the question of whether this bumpiness affects the result.
What we have here is a siphon: if the water is not flowing, the pressure at any point along the hose is simply given by the height of the point relative to the level of the body of water that the inlet of the hose is submerged in. In fact, the pressure will be
$$p = p_0 - \rho g h$$
Where $\rho$ is the density of water (usually 1000 kg/m3), $g$ is the gravitational acceleration (9.8 m/s2) and $h$ is the height above the pond level. As you can see, when $h$ becomes greater than 10 m the pressure will become negative: this means the water will boil (evaporate), creating a bubble in the hose. At that point, the relationship is no longer simple. On the other hand, if the hose goes through a valley, the local pressure will be higher - but this will not matter in the end.
The following is multiple choice question (with options) to answer.
A person takes buckets of water from the house and begins to add it to a pond in the yard. After a certain point, the pond | [
"bloats",
"breaks",
"sinks",
"drowns"
] | A | when a body of water receives more water than it can hold , a flood occurs |
OpenBookQA | OpenBookQA-597 | visible-light, sun, weather
Title: Why are clouds lighter than the sky during the day but darker at night This is probably a very basic question but I couldn't find a good answer to it, most search results are about rain clouds or clouds appearing red at night (something I've never seen except for during sunset but apparently it's common in bigger cities).
Basically what I'm wondering is why clouds during the day appear lighter than the sky (white vs light blue) while clouds at night and during the evening appear darker than the sky (see image).
Image quality is low because I took it with my phone through my window.
I guess the clouds could be blocking the light and therefore appear darker but in that case, shouldn't the same thing be happening during the day? There could be quite a few things going on.
Off the bat there's no incoming light for them to scatter: during the day, clouds are white because the water droplets are big enough for all visible light to cause Mie scattering, but if you don't have much light falling on them, you can't observe the scattering and you can't observe light passing through either.
Then you could consider the fact that in some places, it rains more in the evening/night than during the day (if you have hotter surface temperatures during the afternoon, you see cloud formation and precipitation during the late evening, and with the lower temperatures in the night, the air is more likely to become saturated, see Dew Point), and clouds which precede rain are thicker and denser. They don't allow much light pass through.
And lastly, there's less ambient light which they can reflect back towards you.
The following is multiple choice question (with options) to answer.
What is present during the day but not at night? | [
"the moon",
"sunlight",
"clouds",
"planets"
] | B | if something is outside during the day then that something will receive sunlight |
OpenBookQA | OpenBookQA-598 | zoology, mathematical-models, software, imaging
Title: What would it take to recognize a deer by its photo? I am trying to recognize a deer by its antlers or any other means.
Elaborating:
I was hoping to use their antlers to recognize them but I have heard that most deers shed their antlers every year so it would be difficult to recognize it from the last year's photo unless these antlers retain the same pattern every year.
If not the antlers, what other characteristics should I be looking for?
Is there any software that can help me in recognizing a deer? There is a lot of variation in how and when deer shed their antlers. In most arctic and temperate-zone species, antler growth and shedding is annual, and is controlled by the length of daylight. In tropical species, antlers may be shed at any time of year, and in some species such as the sambar, antlers last several years. Some equatorial deer never shed their antlers.
The horns change every year and, especially, increase the number of branches (and consequently, change their shape). You can't recognize them by antlers, but by other features, such as color of the hair or the lineaments. Like us, animals have individual morphological differences that are recognizable and listable.
Biologists specializing in studies of particular animal species not only take photos, but also make drawings and write descriptions of behavior, to identify individuals within herds.
An optical examination, however, of the subject through drawings and photos (and if possible, direct observation), is more useful than a PC program. This involves identifying particular similarities and equalities that are not "identical". This is possible to do visually on a large (but limited) number of specimens. The human eye is the best computer.
The following is multiple choice question (with options) to answer.
A deer | [
"would live in an area devoid of fauna or flora",
"would live in an area surrounded by redwoods",
"would live in a highly populate city",
"would live in an aquatic environment"
] | B | a deer lives in a forest |
OpenBookQA | OpenBookQA-599 | electromagnetism, geophysics, geomagnetism
Title: Why is modelling the Earth as having geomagnetic poles useful? I'm reading about geomagnetic poles and wondering what their signifcance is. It seems one (and perhaps the main) purpose of using this type of model is for understanding the aggregation of magnetic particles from outside of earth. I feel as though I'm missing a step as to why this model is used, surely the magnetic particles from space still experience the irregular magnetic field of earth?
My guesses from the reading I've done so far are that:
At a great distance, the magnetic particles do actually experience equivalent attraction as though the Earth had a bar magnet that gave it its geomagnetic poles.
Over some time period, and over a number of particles the force experienced by all particles averages to what would be experienced if the Earth had a bar magnet that gave it its geomagnetic poles.
The following is multiple choice question (with options) to answer.
Earth's magnetic patterns are helpful | [
"to birds building a nest",
"to lions roaming the Sahara",
"to birds looking a warmer locale",
"to whales trying to find a mate"
] | C | Earth 's magnetic patterns are used for finding locations by animals that migrate |
OpenBookQA | OpenBookQA-600 | fluid-dynamics, pressure, ideal-gas, bernoulli-equation
Title: Bernoulli's principle at molecular level I've seen many questions and answers about this topic, which keep saying that pressure decrease is the cause of acceleration of flow, and don't explain where that pressure drop comes from in the first place, while others say that pressure drop is just due to energy conservation as the flow speeds up.
My question is regarding ideal gases at low speeds. So, what is the actual reason that causes a drop in pressure (maybe explain it at molecular level), because if pressure is calculated from this relation: $PV=nRT$, and we don't observe a decrease in any of those factors, that would cause a drop in pressure. Also, given that pressure of a gas is due to collision of molecules with the walls and themselves, how does pressure decrease in terms of collision between surface and themselves?
Also, why don't we observe a drop in temperature if, in free gas expansion, the temperature drops momentarily as it gets turned to kinetic energy of flow, and then temperature returns back to normal as the kinetic energy of flow converts back. Why doesn't the same happen in this case?
if pressure is calculated from the this relation : $PV=nRT$ and we don't observe a decrease in any of those factors that would cause a drop in pressure
This statement is not true. $P$, $V$ do change, and $T$ may change as well. Let's see why:
The classical example of accelerated flow is when a fluid (make it an ideal gas for simplicity) flows adiabatically through a converging nozzle:
The following is multiple choice question (with options) to answer.
Descending air pressure leads to | [
"a lower chance of rain",
"an ascending chance of showers",
"a decreased likelihood of showers",
"has zero effect on the weather forecast"
] | B | as air pressure decreases , the chance of rain will increase |
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