question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>I am working on the following problem:</p>
<p>The braking acceleration for a car based on data in a driver’s handbook is –12.2 m/s2. If the car has a mass of 925 kg, find the frictional force and state the direction. </p>
<p>So far I have done the following:
F = ma
F = (925)(-12.2)
F = -11285N</p>
<p>I believe th... | g10929 | [
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<p>I am having trouble getting from one line to the next from <a href="http://en.wikipedia.org/wiki/Screened_Poisson_equation" rel="nofollow">this</a> wiki page. I am referring to the text line </p>
<blockquote>
<p><em>Green's function in $r$ is therefore given by the inverse Fourier transform,</em> </p>
</blockquo... | g10930 | [
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<p>I don't know about all the details of Bell tests using methods like parametric down conversion, but at least in some versions of the EPR paradox you get two photons moving apart in opposite directions. I wonder if you can look for detection coincidences by using photographic plates instead of coincidence counters? T... | g10931 | [
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<p>Is it possible to check from the EM waves(basically Light rays), if there are any extraterrestrial objects interference/passage during its travel from the Sun? I mean, can these EMs from the Sun be visually reproduced to pictures to see what has happened to these waves en route from the Sun? </p> | g10932 | [
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<p>Is it possible to calculate the weight of a person by only
using his smartphone, some action he must perform (jump, rotate etc.) and
some data like his height or age.</p>
<p>Current smartphones have the following sensors/instruments:
G-Sensor
Digital compass
Proximity sensor
Ambient light sensor
GPS</p>
<p>In conj... | g10933 | [
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<p>I'm trying to calculate coexistence curves and get a rough estimate for the critical point of simple fluids using the well-known Gibbs Ensemble Monte Carlo (GEMC) (c.f. Panagiotopoulos, Molecular Physics 61 1987). In doing so, my test has been the square-well potential (SW) since there exist numerous literature data... | g10934 | [
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<p>There is a closed system that is just a windmill attached to a rotating shaft that can mechanically power something. I know the system produces work on the surroundings from the rotating shaft and this is positive work, but is there also a negative work input from the wind pushing the blades of the windmill?</p>
<p... | g10935 | [
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<p>suppose you place a number of rotating black holes in linear sequence (rotating around the same axis) between two stars at distance $d$ (assume as tightly packed as practical for purposes of calculation). If a ship enters each ergosphere and goes out into the next one, can it make the roundtrip back to home in less ... | g10936 | [
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<p>What are those white lines connecting the ground to the sky on the left side of this photo?</p>
<p>I've see these before in the nuclear bomb test films too. They're apparently already in place upon detonation, as the bright backlight from the mushroom cloud suddenly makes these lines appear in the foreground.</p>
... | g10937 | [
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<p>I usually think of gravitational potential energy as representing just what it sounds like: the energy that we could potentially gain, using gravity. However, the equation for it (derived by integrating Newton's law of gravitational force)...</p>
<p>$PE_1 = -\frac{GMm}{r}$</p>
<p>..has me thrown for a loop, espe... | g27 | [
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<p>The <a href="https://en.wikipedia.org/wiki/Poynting_vector" rel="nofollow">Poynting vector</a> is a representation of the <a href="https://en.wikipedia.org/wiki/Energy_flux" rel="nofollow">energy flux</a> in electromagnetics, showing the amount and direction of power flow at different points in space. In electric c... | g10938 | [
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<p>I'm not new to QFT, yet there are some matters which are quite puzzling to me. I often come across the statement that real particles (the ones we actually measure in experiments, not virtual ones) are "slightly off-shell". What does this actually mean? To my knowledge, something being off-shell means that it violate... | g10939 | [
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<p>If we were to build a high speed rail up the side of a mountain like in some ScFi movies, what is the velocity needed at the point of living the mountain excluding angular momentum from earth’s rotation to achieve escape velocity?</p> | g10940 | [
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<p>Why <em>should</em> the mass of elementary particles be theoretically of the magnitude of the Planck mass?</p>
<p>I've read that already a few times but I don't understand why it should be that way.</p>
<p>For example: Zwiebach - <em>A first course in string theory</em>, p.55</p>
<blockquote>
<p>If the fundamen... | g10941 | [
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<p>If a particle in a delta potential well has negative energy, why the particle will be bound in the well? And if it has positive well, why it is free to move in either half-space: x < 0 or x > 0?</p>
<p>I just read these in a wikipedia page:
<a href="http://en.wikipedia.org/wiki/Delta_potential" rel="nofollow">ht... | g10942 | [
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<p>What effect does the quantum world have on radio waves? For example, if I could shrink myself down and stand on the nucleus (or even smaller sub atomic particles making up the nucleus) with a device which could measure radio waves of the surrounding world (ie with all the signals modern day humanity produces), what ... | g10943 | [
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<p>I am reading Landau's Volume 2 of the course of theoretical physics. I have a doubt after reading the first few pages of it which I explain below.</p>
<p>Landau first defines intervals and on pages 5 and 6 shows that two events having time like interval between them can never occur simultaneously in any reference s... | g10944 | [
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<p>How would the quantum mechanical treatment of the moon as a gravitationally-bound object differ from the usual treatment of the hydrogen atom using Schrödinger's equation?</p>
<p>[The earth's gravitational potential V(r) = -GM/r where M is the mass of the earth: 6 x 10<sup>24</sup> kg. The mass of the moon is 7.4 x... | g10945 | [
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<p>Let me justify my question before I go on. In string theory, gravitons are strings extended over space. Longitudinal gravitons are pure gauge modes of the diffeomorphism group. However, in string theory, longitudinal gravitons are also extended objects. A condensate of longitudinal gravitons is equivalent to a diffe... | g10946 | [
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<p>Why when we quantize EM field, whe quantize the vector potential $A^\mu$ obtaining vectorial particles (photons) like the elastic field (phonons) and we can't quantize directly the EM-field tensor $F^{\mu\nu}$? We in that situation should obtain tensorial particles of spin 2 like graviton..It's wrong? Why?</p> | g10947 | [
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<p>Why is using a <a href="http://en.wikipedia.org/wiki/Wheatstone_bridge" rel="nofollow">Wheatstone bridge</a> such an accurate way of calculating an unknown resistance? What are the benefits of using it over Ohm's law?</p>
<p>It seems that it has something to do with the wires heating up during ohm's law calculation... | g10948 | [
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<p>According to general relativity, speed is relative, so for example if you are running at
20 km/h and a car passes you at 30 km/h, the runner is actually moving at 50 km/h relative to the car.</p>
<p>Now imagine that 2 spaceships are traveling both at 99% the speed of light, and they pass each other in a linear fas... | g109 | [
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<p>I am trying to compute the $\vec{E}$ and $\vec{B}$ fields in the Axial gauge ($n \cdot \vec{A}=0$) where $n^2=1$, but I'm having trouble seeing the usefulness/how it simplifies the equations.</p> | g10949 | [
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<p>Doesn't lead, according to its electron configuration, have unpaired electrons? Yet why isn't it paramagnetic?</p> | g352 | [
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<p>I have two related questions that I would like help on:</p>
<ol>
<li><p>When a power plant creates power like the <a href="http://en.wikipedia.org/wiki/Electricity_generation" rel="nofollow">Hoover Dam</a>, it can provide 2.07 GW of electrical power. My question is what does this mean? I assume from Faraday’s law t... | g10950 | [
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<p>I have following exercise:
If $[C,D]$ is a c-number and $f(x)$ is a well-behaved function (i.e. all derivatives exist and are finite), show that:
$$[C, f(D)]=[C,D]f'(D)$$
where $f'(D) = \frac{d}{dx}f(x)$</p>
<p>I used expansion:
$$f(D) = \sum_{k} a_k D^k $$
that way:
$$\sum_k a_k [C,D^k]=\sum_k a_k k [C,D]D^{k-1}$... | g10951 | [
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<p>A recent estimate by the Kavli Institute for
Particle Astrophysics and Cosmology (a joint
institute of Stanford and SLAC) is that there
are <a href="http://news.stanford.edu/news/2012/february/slac-nomad-planets-022312.html" rel="nofollow">circa 100000 times as many 'nomad planets' as stars</a></p>
<p>I found "<... | g10952 | [
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<p>In Einstein A., Zur Quantentheorie der Strahlung, Phys.ZS., 18, 121-137 (1917) spontaneous emission is considered to occur together with induced radiation so that one can write the following condition for equilibrium (which also includes induced absorption): $$ p_n e^{-\frac{\varepsilon_n} {kT}} B_n^m \rho = p_m e... | g10953 | [
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<p>This is a <em>very</em> basic question about the concepts of force and acceleration. Consider the following situations:</p>
<ol>
<li>I sit on the floor of my room on earth</li>
<li>I sit on the floor of a spaceship that accelerates with 1g (in a direction perpendicular to its "floor")</li>
</ol>
<p>In both situati... | g10954 | [
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<p>In Landau course, vol.1 Mechanics, one finds the statement: </p>
<blockquote>
<p>...the absoluteness of time necessarily implies that the ordinary law of composition of velocities is applicable to all phenomena.</p>
</blockquote>
<p>I don't see this implication clearly.</p> | g10955 | [
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<p>What is it about conformal transformations that make them so widely applicable in physics?</p>
<p>These preserve angles, in other words directions (locally), and I can understand that might be useful. Also, I gather this is equivalent to scale invariance, which seems like another handy feature.</p>
<p>Are those th... | g10956 | [
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-0.015413722954690456,
-0.01949138566851616,
-0.013743655756115913,
0.02652941644191742,
0.00... |
<p>If you want to maximize the maximum velocity a child could go, what would be the optimum height?</p>
<p>If you wanted to maximize the efficiency of a child "pumping" their legs to gain velocity, what would be the optimum height?</p>
<p>I hope that I am correctly understanding how a child pumping their legs makes i... | g10957 | [
0.02980293519794941,
0.06778306514024734,
0.016594858840107918,
0.011006881482899189,
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0.04874091222882271,
0.030231215059757233,
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-0.0013184086419641972,
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-0.0251353457570076,
-... |
<p>What is the permeability of magnesium sulphate and therefore the magnetic susceptibility?</p> | g10958 | [
-0.044979870319366455,
0.02554214932024479,
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0.031142713502049446,
0.034... |
<p>In this paper,</p>
<blockquote>
<p>Localization of an atom by homodyne measurement. A. M. Herkommer et al. <a href="http://dx.doi.org/10.1088/1355-5111/8/1/014" rel="nofollow"><em>Quantum Semiclass. Opt.</em> <strong>8</strong> no. 1, p. 189 (1996)</a> (paywalled).</p>
</blockquote>
<p>the authors are able to lo... | g10959 | [
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0.014733601361513138,
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0.04973062872886658,
-0.003828219138085842,
-0.019472980871796608,
0.014235739596188068,
-0.02559497579932213,
-0.003940104972571135,
... |
<p>How to get energy of collision if you know force of gravity of an object($m \rightarrow F=mg$)?
You get energy of collision by kinetic energy $E_k= \frac{1}{2}mv^2$, but if you use just force of gravity($F=mg$), how you get then the energy of collision? I know that work(energy?) $W$ made by object is $W=F \Delta s$,... | g10960 | [
0.029980117455124855,
0.05473249778151512,
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0.05583479627966881,
-0.... |
<p>According to wikipedia, <a href="http://en.wikipedia.org/wiki/List_of_moment_of_inertia_tensors" rel="nofollow">the inertia tensor of an ellipsoid</a> with semi-axes $a,b,c$ and mass $m$ is </p>
<p>$\left[\begin{array}{ccc}
\frac{m}{5}(b^2+c^2)&0&0\\
0&\frac{m}{5}(a^2+c^2)&0\\
0&0&\frac{m}{5... | g10961 | [
0.023998958989977837,
0.05286230891942978,
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0.0335455983877182,
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0.010284552350640297,
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0.02038176730275154,
-0.061... |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/7823/is-time-travel-possible">Is time travel possible?</a> </p>
</blockquote>
<p>Is time travel possible? According to my friend, it is possible to go to the future but not the past. </p>
<p>In Physics,... | g104 | [
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0.00847153551876545,
0.037150196731090546,
0.05118175595998764,
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0.012762698344886303,
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0.009952894411981106,
0.041363269090652466,
-0.... |
<p>Suppose that we have two fluids $A$ and $B$ in a container $\Omega$, and we notice that $A,B$ do not mix. </p>
<ul>
<li>Can you pleas explain to me what is the cause of this property?</li>
<li>What properties of the two fluids create the superficial tension between them? </li>
<li>Is the superficial tension between... | g10962 | [
0.04772379994392395,
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-... |
<p>I'm studying for a test of static rigid body and I'm having doubts on how to solve problems involving levers with weight.
If I have, for example, a lever 10 kilograms and 3 meters long and one support point at 1 meter from one end, how much force must be applied to the other side to achieve equilibrium?</p> | g10963 | [
0.044242389500141144,
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0.06237810105085373,
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<p>Suppose someone manages to evaluate the string theory $S$-matrix to all orders for any and all vertex operator insertions including non-perturbative contributions from world-sheet instantons and re-sum the whole series to obtain the exact non-perturbative string theory $S$-matrix for any combination of in- and out-s... | g10964 | [
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<p>I read this intriguing statement in <a href="http://math.ucr.edu/home/baez/twf.html" rel="nofollow">John Baez' week 197</a> the other day, and I've been giving it some thought. The post in question is from 2003, so I was wondering if there has been any progress in formulating or even settling the conjecture in the t... | g10965 | [
0.005552520044147968,
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0... |
<p>Consider $N=4$ super-symmetric gauge theory in 4 dimensions with gauge group $G$. As is explained in the beginning of the paper of Kapustin and Witten on geometric Langlands, this
theory has 3 different topological twists. One was studied a lot during the 1990's and leads
mathematically to Donaldson theory, another ... | g10966 | [
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0.008888544514775276,
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0.057451032102108,
-... |
<p>What exactly does it imply about a condensed matter system to have particle number conserved or not conserved?</p>
<p>For example, why does the superconducting phase break particle number conservation while the insulating phase does not? What exactly brings about the breaking of this conservation?</p> | g10967 | [
0.020890187472105026,
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0.06338512897491455,
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0.023032... |
<p>My question is very simple: Are there any interesting examples of number theory showing up unexpectedly in physics?</p>
<p>This probably sounds like rather strange question, or rather like one of the trivial to ask but often unhelpful questions like "give some examples of topic A occurring in relation to topic B", ... | g10968 | [
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0.05263741314411163,
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0.026966549456119537,
0.02... |
<p>Ptolemy's model of universe assumes that our earth is the static center of universe and everything else move relative to it (ref: <a href="http://en.wikipedia.org/wiki/The_Grand_Design_%28book%29" rel="nofollow">The grand design</a> ch:3). This model would give us a consistent picture of universe the only complicati... | g10969 | [
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0.0165... |
<p>I was using Waves - Berkley Physics Volume III, and in explaining Snell's Law the author claims that as a wave is on the boundary between glass and air (going from glass to air) that the number of wave crests per unit length along the $y$-axis must be equal in both mediums.</p>
<p>I still don't understand this clai... | g10970 | [
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0.0213... |
<p>An object of mass $m = 5.00 g$ is moving at constant velocity $v_0 = 3.10 m/s$. At $t = 0$ and
$x = 1.50 m$, it is subjected to a resistive force $F_{res} = −mbv^2$ where $b = 0.520 m^{−1}$
is a constant. (Assume that the initial velocity is pointing in the positive direction.)</p>
<p>Express the velocity as a fun... | g10971 | [
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0.0495869405567646,
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0.044348087161779404,
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0.0049... |
<p>Take a <em>classical</em> field theory described by a local Lagrangian depending on a set of fields and their derivatives. Suppose that the action possesses some global symmetry. What conditions have to be satisfied so that this symmetry can be gauged? To give an example, the free Schrödinger field theory is given b... | g10972 | [
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0.024102812632918358,
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0.056287337094545364,
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-0... |
<p>I have just basic understanding of Physics from elementary school. But I still wonder, why after 10 years of cameras in cellphones, there is no "small-pack" optical zoom.</p>
<p>I think there should be no problem to make small, but still precise lenses. It should not be a problem to make small light sensor, while k... | g10973 | [
0.029744181782007217,
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-0.03909813240170479,
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0.038165464997291565,
... |
<p>I took this photo. Above the horizon there is a thick layer that looks like a cloud, but it surely isn't. Is this a <a href="http://en.wikipedia.org/wiki/Fata_Morgana_%28mirage%29">Fata Morgana</a>? What do you think?</p>
<p>EDIT: I think the more appropriate name is <a href="http://en.wikipedia.org/wiki/Mirage#Sup... | g10974 | [
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0.025264659896492958,
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-0.0... |
<p>Can someone name a paper or book which calculates the critical temperature of the Ising model from scratch? It might be a book and should contain the necessary prerequisites. I have had a basic course in stat physics and thermodynamics.</p>
<p>Edit:
The two suggested books have 500 pages of preface, is this necessa... | g10975 | [
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0.04810590669512749,
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0.01893501542508602,
0.07182615250349045,
-0.042... |
<p>What materials cause radio waves to refract? What are the radio IOR's of these materials?</p> | g10976 | [
0.03589591383934021,
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0.04698752611875534,
0.07316336035728455,
-0.03810079023241997,
0.007161... |
<p>Recently I read that some results are obtained in directions of tricking the uncertainty principle. The relevant link is here: <a href="http://www.caltech.edu/content/tricking-uncertainty-principle" rel="nofollow">http://www.caltech.edu/content/tricking-uncertainty-principle</a> , and the paper is on the Arxiv.</p>
... | g10977 | [
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0.02783658355474472,
0.005443681962788105,
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-0... |
<p>I've read that Wilson lines are the effective degrees of freedom for high-energy partons, when you consider collinear gluon emission. But I'm struggling to find a readable account of this topic. Does anyone have suggestions?</p> | g10978 | [
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-0.0333294495940208... |
<p>For photons (and any massless particle) we consider only a spin projection into the direction of motion (helicity). Why it's meaningless to talk about projection of photon's spin into some arbitrary direction? Is this because we can't measure it (photon does not have a rest frame)?</p> | g10979 | [
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-0... |
<p>I understand the physical meaning of electrostatic energy of a system of charges (or a distribution with given density) as the energy stored in the system while working to carry the charges from infinity to their actual place in the system. According to <a href="http://en.wikipedia.org/wiki/Electric_energy" rel="nof... | g10980 | [
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0.02089555375277996,
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0.04458972066640854,
-0.04637... |
<p>Recently an experiment was performed in which myself and a partner filled a water balloon and threw it back and forth at each other without breaking it. We gradually increased the distance at which it was being thrown and at one point I ended up on the second floor of one of my high school buildings and when I threw... | g10981 | [
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0.0182218998670578,
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-0.034... |
<p>I've done an intro course on QM and I'm now hoping to understand exactly how to use probability theory rigorously in solving problems. My question is: <strong>How do I do the same thing, or the closest thing possible, in <a href="http://en.wikipedia.org/wiki/Quantum_mechanics" rel="nofollow">quantum mechanics</a>?</... | g10982 | [
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0.005570678971707821,
0... |
<p>I'm confused by <a href="http://en.wikipedia.org/wiki/Airfoil" rel="nofollow">wikipedia's page on aerofoils</a>, the <a href="http://en.wikipedia.org/wiki/Aerodynamic_center" rel="nofollow">aerodynamic center</a>, and <a href="http://en.wikipedia.org/wiki/Center_of_pressure_%28fluid_mechanics%29" rel="nofollow">cent... | g10983 | [
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0.03040996380150318,
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0.011928440071642399,
-... |
<p>I have calculated that because Venus is $d = 12,103.6~\mathrm{km}$ in diameter and moves at $v = 35.02~\mathrm{km}/\mathrm{s}$, it would take
$$ t=\frac{d}{v} = \frac{12,103.6~\mathrm{km}}{35.02~\mathrm{km}/\mathrm{s}} = 345.62~\mathrm{s} = 5~\mathrm{min}~46~\mathrm{s} $$
for Venus to appear totally in front of the ... | g10984 | [
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0.026074834167957306,
0.04402414709329605,
-0.0113... |
<p>I'm thinking about starting my work of physics with this question but do not know how to answer.</p> | g10985 | [
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0.011982920579612255,
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0.0060... |
<p>If I take a closed circuit with two capacitors and a voltage difference, the circuit is apparently in parallel, but if I introduce a battery, the circuit is in series. Why does the presence of the battery make a difference? </p>
<p>Here's a diagram of what I mean:</p>
<p><img src="http://i.stack.imgur.com/CRwHQ.pn... | g10986 | [
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0.03820008039474487,
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-0.02621830441057682,
-0.06035023555159569,
0.06636394560337067,
-0.041547320783138275,
0.0342... |
<p>Consider a scalar field doublet $(\phi_1, \phi_2)$ with a Mexican hat potential </p>
<p>$$V~=~\lambda (\phi_1^2+\phi_2^2-a^2)^2.$$</p>
<p>When $a=0$ this is a quartic potential and the symmetry is not spontaneously broken. However when the field acquire a VEV, the fields splits into a massive mode and a massless b... | g10987 | [
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<p>I'm trying to plot a maxwell-boltzman velocity distribution in matlab. </p>
<p>I have also asked this question at cross validated without much luck</p>
<p>The PDF is </p>
<p>f(v)=sqrt(m/2*pi*k*T) * exp(-m*v^2/2*k*T)</p>
<p><a href="http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution" rel="nofollo... | g10988 | [
0.0315997377038002,
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<p>So I guess I don't really understand the situation in question... I heard a radio piece about the <a href="http://en.wikipedia.org/wiki/Costa_Concordia">Costa Concordia shipwreck</a> in Italy taking 7-10 months to remove the vessel from its place of resting, and I was reminded of the <a href="http://www.iusmentis.co... | g10989 | [
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<p>When a substance changes state from solid to liquid, the temperature of the substance remains the same and the heat energy from the external source is converted to potential energy within the substance.</p>
<p>My question is that If I think of it in the reverse direction, I mean when the state changes from liquid t... | g10990 | [
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<p>I am designing a "glider" of sorts, and I have some basic questions about the physics involved to get me started. How much lift is required to overcome the weight of an average person, say 150 pounds? Is the lift required simply 150 pounds?</p> | g10991 | [
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<p>Sometimes when I bicycle against hard wind, I find it difficult to breathe. Others I have discussed it with have also noticed this effect.</p>
<p>A possible related phenomenon that I heard from an acquaintance who went motorcycling in Arizona was that when it was really hot, he had to drive very slowly in order to ... | g10992 | [
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<p>I was wonder why cameras the good ones have two lenses instead of one?</p>
<p>what benfit does it carry with this fact?</p>
<p>I have told that old cellular phones have camera with one lens and hence it blurring the </p>
<p>picture, why is that? and why 2 or more lenses are solving this or other problems?</p>
<p... | g10993 | [
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<p>A couple of weeks ago I was travelling in a car (120 km/h approximately) and I saw a <a href="http://en.wikipedia.org/wiki/Fly" rel="nofollow">fly</a> flying in front of me (inside the car, near my nose, windows closed). I wonder how was that possible. </p>
<p>Does it mean is really flying at 120 km/h or the fly is... | g432 | [
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<p>I'm planning on getting into research in mathematical physics and was wondering about interesting topics I can get into and possibly make some progress on. </p>
<p>I'm particularity fond of abstract algebra and topology and if possible any topics that involve abstract algebra would/topology/calculus of variations w... | g10994 | [
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<p>I was browsing through <a href="http://arxiv.org/abs/gr-qc/0108040">this</a> and was wondering what progress in <a href="http://en.wikipedia.org/wiki/Quantum_gravity">quantum gravity</a> research has taken place since the (preprint) publication.</p>
<p>If anyone can provide some helpful feedback I would be greatly ... | g10995 | [
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<p>One formulation of Maxwell's Gauss Law for electric field is:</p>
<p>$$\bigtriangledown E = 4 \pi k \rho $$</p>
<p>This can be worked into the Divergence Theorem as follows:</p>
<p>$$\int\int_{A} F_\perp \:dA= 4\pi k \int\int\int_V \rho\:dV$$</p>
<p>As far as I can tell, the "outward pointing area normal" $F_\pe... | g10996 | [
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<p>(Probably related to <a href="http://physics.stackexchange.com/questions/721">this one</a>, and probably should be CW.)</p>
<p>A very long time ago, I had the good fortune to read George Gamow's excellent series of <em>Mr. Tompkins</em> books. That introduced me to the idea of a world where the usual physical const... | g10997 | [
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<p>I'm working on low budget small solar power project.</p>
<p>I want to transport heat (peak heat power about 1kW) over ~10 meter (~30ft) long pipe or hose.</p>
<p>I was thinking about thin hose (6-8mm / about 1/4 inch inner diameter ) to keep small surface area and make water flow faster (and loose less energy) - <... | g10998 | [
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<p><img src="http://i.stack.imgur.com/PF3Z7.jpg" alt="enter image description here"></p>
<p>(Zoom in <a href="http://i.stack.imgur.com/PF3Z7.jpg" rel="nofollow">here</a> to see the scales.)<br>
About the result of plotting running of 3 coupling constant, we think that we should get the correct one(MSSM).</p>
<p>But w... | g10999 | [
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<p>I am trying to compute the amount of energy released in the form of heat if I compress 1 cubic meter of Hydrogen to 0.1 cubic meter while submerged in a large body of water of a given temperature - say 300 degrees Kelvin.</p>
<p>Would someone smarter that I am be able to show me the appropriate formula and the comp... | g11000 | [
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0.02156214602291584,
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<p>I have solved the Killing vector equations for a 2-sphere and got the following answer. $A,B,C$ are three integration constants as expected.</p>
<p>$$\xi_{\theta}=A \sin{\phi}+B\cos{\phi}$$
$$\xi_{\phi}=\cos{\theta} \sin{\theta}(A \cos{\phi}-B\sin\phi)+c \sin^2{\theta}$$</p>
<p>From this, how do I find the basis e... | g11001 | [
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<p>So I know that $V=IR$ works for circuits, but for the case of an arc-before the arc jumps, there is a potential difference, but no current, but there isn't infinite resistance is there?
I don't understand how to compute a finite resistance for an arc that would come out as infinite in some other cases.</p> | g11002 | [
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<p>Assuming Minkowski spacetime, we know that the longest proper time curve joining two points is the rect joinining both events, While the shortest time-like curve is not a compact set (because there are sequences with limits that do not belong to the set) the proper acceleration is unbounded in such curves.</p>
<p>M... | g11003 | [
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0.009096318855881691,
0.006642229855060577,
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<p>I am using Di Francesco's book P.39. The equation that the generators of the transformations satisfy is given by: $$iG_a \Phi = \frac{\delta x^{\mu}}{\delta w_a} \partial_{\mu} \Phi - \frac{\delta F}{\delta w_a},$$ where $\left\{w_a\right\}$ are a set of parameters for the transformation and $G_a$ is the correspond... | g11004 | [
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<p>I am an amateur of experimental physics, and I would like to use a Stanford dual sr400 counter to make the photons coincidence counting to see quantum optical effects. Right now I am about to set up an optical experiment. </p>
<p>I have questions about the coincidence counting of my counter:</p>
<p>First of all, ... | g11005 | [
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0.03536362946033478,
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0.0220... |
<p>I'm looking for a reference (books, notes, lectures) which helps a physicist to understand the language of measure theory in the context of stochastic processes (in particular markov chains).</p>
<p>I've studied markov chains and measure theory but now I'm looking for something which helps me filling the gap and ma... | g11006 | [
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<p>I already apologize for my medium english... I'm a french guy, not really gifted to recognize electronic circuits :</p>
<p>In fact, I need to identify a circuit from is function. So, here is the block (called OCT)</p>
<p><img src="http://i.stack.imgur.com/azzeG.jpg" alt="enter image description here"></p>
<p>I on... | g11007 | [
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0.051908940076828,
0.00559590570628643,
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<p>I am trying to get my hands on an English or German translation of the seminal work by Gauss on fluid shapes in equilibrium: "Principia generalia Theoriae Figurae Fluidorum in statu Aequilibrii [General principles of the theory of fluid shapes in a state of equilibrium]" from 1830.</p>
<p>I have found a <a href="h... | g11008 | [
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0.04168214276432991,
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0.03749159723520279,
-... |
<p>Suppose we have two wheels attached to axis (each wheel has its own axis). One wheel is heavy compared to the other. The moment arm of force is same for the both wheels. A force F is applied on both the wheels. The applied force is also same for both wheels.</p>
<p>The light wheel will rotate fast compared to the h... | g11009 | [
0.025916194543242455,
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0.028354262933135033,
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<p>How to solve the <a href="http://en.wikipedia.org/wiki/Ising_model" rel="nofollow">Ising model</a> in <a href="http://en.wikipedia.org/wiki/Ising_model#One_dimension" rel="nofollow">1D</a> by low temperature, and high temperature expansion, and by change of variable method? Can you please give me some reference link... | g11010 | [
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0.018913663923740387,
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0.019605204463005066,
0.00747752794995904,
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0.01706118881702423,
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0.056702446192502975,
0.03875255584716797,
0.0247... |
<p>My nephew showed me an exercise from his school-textbook about boiling eggs. Here is the exercise (translated from german):</p>
<ol>
<li>To make one hard-boiled egg in a pot of water one has to put it for 8 minutes into boiling water. How long does it if you put 10 eggs into the boiling water instead of one to make... | g11011 | [
0.04971623048186302,
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0.001059815171174705,
0.01188796665519476,
0.006204598117619753,
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0.031536079943180084,
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0.01658325083553791,
0.046617407351732254,
0.054... |
<p>Suppose I had a ray of unpolarized light, and I was sitting inside the beam and looking at the electric fields oscillating, then , if I am looking at a point how would the oscillations look like? I cannot seem to understand it.</p> | g11012 | [
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<p>One problem that I'm having trouble with (as opposed to the other):</p>
<blockquote>
<p>The Messenger is a probe that orbits Mercury $700 \rm km$ from the surface. What is the tangential velocity it should be rotating at so that it doesn't precipitate towards the planet, in $\rm m/s$? </p>
<p><strong>Data</s... | g11013 | [
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0.026264779269695282,
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0.05045616999268532,
0.0093226945027709,
... |
<p>The following is the extract from <a href="http://www.nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-lecture.pdf" rel="nofollow"><em>Albert Einstein's lecture</em></a> to the Nordic Assembly of Naturalists (July 11, 1923). </p>
<blockquote>
<p><em>If we consider that part of the theory of relativity... | g11014 | [
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0.07892496138811111,
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0.049... |
<p>I have been chewing up some time ago the Schottky-Mott theory of Schottky Barrier height (which ignores the surface states). All the deduction seems to ground on fundamental thermodynamical principles (as the equality of Fermi levels- i.e. equality of chemical potential in equilibrium) but there is something which I... | g11015 | [
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0.0018265241524204612,
... |
<p>For a single particle or field, I can't see how the <a href="http://en.wikipedia.org/wiki/Path_integral_formulation" rel="nofollow">path-integral formulation</a> depends on the order of terms in the Lagrangian. It seems that you integrate the classical Lagrangian to get the action on a path, then integrate over all ... | g353 | [
0.07973114401102066,
0.037374347448349,
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<p>Suppose that a force acting on a particle is factorable into one of the following forms:</p>
<p>$$\text{a)}\,\,F(x_{i},t)=f(x_i)g(t)\,\,\,\,\,\,\,\text{b)}\,\,F(\dot{x}_{i},t)=f(\dot{x}_{i})g(t)\,\,\,\,\,\,\text{c)}\,\,F(x_{i},\dot{x}_{i})=f(x_i)g(\dot{x}_i)$$</p>
<p>for which cases are the equations of motion int... | g11016 | [
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<p>I heard that electrons accumulate at points on metals, and this clearly explains the arcing phenomenon, but how does a microwave make an electron imbalance on the fork?</p> | g369 | [
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0.052... |
<p>I am wondering about size of <a href="http://en.wikipedia.org/wiki/Black_hole" rel="nofollow">black hole</a>. How is it possible that we have black holes of different sizes? As I know the singularity is point which is infinite small and is infinite dense. So my question is how can infinite dense and infinite small o... | g11017 | [
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<p>A pulley having some mass has a massless string around it, with two unequal masses at the end of the string. Sufficient friction is present between pulley and the string such that the string does not slip on the pulley .</p>
<p>The tensions in the massless string on the two sides of pulley will be same or different... | g11018 | [
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0.00981951504945755,
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0.013288142159581184,
... |
<p>Consider this situation:</p>
<p><img src="http://s3.amazonaws.com/answer-board-image/c4e9ecd2-b064-4e0f-8e5a-f938f98d2e6a.jpeg" alt="Diagram of box on ramp"></p>
<p>When the box is at the bottom of the frictionless incline, it will have a velocity of $v_f$. The person is an inertial frame of reference that moves ... | g11019 | [
0.09509561210870743,
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<p>In a book of "LES HOUCHES - Critical Phenomena, Random systems, Gauge theories" the author Frolich says that:</p>
<p><strong>2D</strong></p>
<blockquote>
<p>In two dimensions, the mean energy of an isolated point defect in a square area of diameter $L$ is proportional to $\log(L)$. The total number of possible p... | g11020 | [
0.03315597400069237,
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<p>From the Gutemberg-Ricther law we know that the frequency of an earthquake is a power law so virtually any magnitude is possible on earthquake event. But the earth has a finite size so there must be an upper theoretical limit on the earthquake's magnitude. Which is this upper limit?</p> | g11021 | [
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0.023424597457051277,
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0.0002831123420037329,
-... |
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