question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>Basically, given a set of noisy observations for the apparent magnitude of a Cepheid variable, how is this fit to a curve which allows the period, and therefore distance, to be found? Cepheids' luminosity isn't sinusoidal. My first though was to use a Fourier approximation, i.e. fit using least sqaures error to $$L(... | 6,471 |
<p>I couldn't find the definition of a Nicolai map. </p>
<p>What is it and what is a simple example which helps understanding it?</p> | 6,472 |
<p>Are the boundaries of a black hole, the event horizon, similar to the boundary at the end of our observable universe?</p> | 6,473 |
<p>I have the usual equations of electrostatics in macroscopic media expressed in Gaussian units:</p>
<p>$$\nabla\cdot\vec{D}=4\pi\rho$$
$$\nabla\times\vec{E}=0$$
$$\vec{D}=\vec{E}+4\pi\vec{P} \tag1$$</p>
<p>My teacher wants me to convert these Equations to the SI system using the following transformation rules:</p>
... | 6,474 |
<p>This is a question I have heard quite some contrary opinions, so I want to ask it here, as it deals with physics in principle:)</p>
<p>The question is basically that, if having a unheated intermediate (in between) will reduce the insulation as compared to a direct outside wall?</p>
<p>This might be a little abstra... | 6,475 |
<p>I've read something about this and I conclude that it happens because of the <a href="http://en.wikipedia.org/wiki/Uncertainty_principle" rel="nofollow">uncertainty principle</a>. But I don't understand very well the meaning of that.<p></p>
<p>I mean, it's very abstract that the speed, $\vec{v}(t)$, and position, $... | 6,476 |
<p>I am interested in knowing how much is one eV of energy. Everywhere I found are the technical definitions. Can anybody please tell me how much is this much energy. I need something which I can feel. I mean how much work I can do with 1 eV? Can I drive a 1000cc car for 1hour? Any of example in context of real life us... | 6,477 |
<p>A friend of mine claims to have been able to surf the Internet without fuss on a Wi-Fi connection while performing NMR on samples he was analyzing. I would have thought the strong magnets needed for this would have washed out Wi-Fi signals due to the radio waves emitted.</p>
<p>How plausible is his claim?</p>
<p>O... | 6,478 |
<p>Let's imagine the following situation: </p>
<p>At an initial moment $t=0$, a large water drop with diameter for example $D=10\ \text{cm}$ is placed in deep space (Say an astronaut is experimenting). Let's the initial temperature of the drop be moderate $T_0=283 K$ and the drop itself is at rest at $t=0$. What wil... | 6,479 |
<p>How can astronomers say, we know there are black holes at the centre of each galaxy?</p>
<p>What methods of indirect detection are there to know where and how big a black hole is?</p> | 744 |
<p>If one draws a circle on a sphere and measures the ratio of the diameter to the circumference, that value varies depending on the diameter of the circle compared to the diameter of the sphere it is drawn on (for a circle much smaller than the sphere it's drawn on, the ratio will converge to $\pi$, whereas for a cir... | 6,480 |
<p>Let's imagine I'm very far from any massive objects, so my local space-time is <a href="http://en.wikipedia.org/wiki/Minkowski_space" rel="nofollow">Minkowskian</a>. Off in the distance is a black hole, far enough away that it doesn't noticeably curve space-time near me, but close enough for me to see it. Its entrop... | 6,481 |
<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Single-mode_optical_fiber" rel="nofollow">single mode</a> and <a href="http://en.wikipedia.org/wiki/Multi-mode_optical_fiber" rel="nofollow">multi mode</a> optical fibres? First off, I guess that by <em>modes</em> we mean the spatial modes of the e... | 6,482 |
<p>Are there any methods of direct detection for black holes?</p>
<p>I'm not referring to gravitational lensing, or measuring the orbits of a star in a binary pair.</p>
<p>Is there any way of directly 'seeing' them? </p> | 6,483 |
<p>Occasionally when I make coffee in my french press I experience something odd. It happens pretty infrequently but certainly enough to be curious about. I have the grounds ready in the carafe. The water just heated in an electric kettle. I pour the water over the grounds and place the plunger on top. Then, maybe... | 6,484 |
<p>Recently I have read one book where there was some incomprehensible proof of the Pauli's spin-statistics theorem. I want to ask about a few details of the proof. </p>
<p><strong>First</strong>, the author derives commutation (anticommutation) relations like $[\hat {\psi} (x), \hat {\psi} (x')]_{\pm}$ for arbitrary... | 6,485 |
<p>I was thinking, if the space is infinite, what if there are infinite number of spaces, inside our universe? I mean, everyone knows that black holes exist, but nobody knows what happens when you get sucked in.</p>
<p>Therefore, I believe that inside the black holes there must be some kind of molecule compression whi... | 6,486 |
<p>I was reading the <a href="http://www.google.com/search?as_q=formalism&as_epq=in+in" rel="nofollow">"in-in" formalism</a> (or "closed time path formalism" used in condensed matter physics) in cosmology created by Schwinger in 1961, and there is a saying： "they care about correlation functions instead of S-matrix... | 6,487 |
<p>Now in disordered organics, the band picture is thrown out the window, from what I can tell (due to lack of symmetry). But don't HOMO/LUMO levels basically take the place of conduction/valence bands in molecules? In a organic system (a lot of molecules with no order), then, I am correct to believe that the HOMO and ... | 6,488 |
<p>I just did a back-of-the-envelope calculation, which surprised me. I calculated the difference in acceleration (due to repelling like-charges) experienced by two sides of an electron the size of the classical electron radius, when placed one angstrom from another electron. I used purely classical formulas:</p>
<p>$... | 6,489 |
<p>I have great trouble in understanding simultaneity in special relativity. Let me illustrate it with a concrete example.</p>
<p>Assuming there is a train, its two end points are $A$ and $B$, the length of the train is $x$. The train moves at speed $v$. Assuming the train is moving in the direction from $A$ to $B$.</... | 6,490 |
<p>I'm curious about how the material absorb the light and reflect the light back as colors in a sense of Quantum Mechanics (Quantum Electro Dynamics)<br>
Does Hadron related to the absorbs of photon ? or are there any other factors ?</p> | 6,491 |
<p>The definition of a Hamiltonian system I am working with is a triple $(X,\omega, H)$ where $(X,\omega)$ is a symplectic manifold and $H\in C^\infty(X)$ is the Hamiltonian function.</p>
<p>I am wondering if someone can give me an interesting, or useful, example of a Hamiltonian system for which $X$ is not the cotang... | 6,492 |
<p>Is there any classical/ quantum mechanical proof for the non-existence of magnetic monopoles?
Or is it just lack of experimental evidence that has led us to the conclusion that monopoles do not exist, when in fact certain other theories predict their existence/ non-existence?</p> | 6,493 |
<p>Okay, some textbooks I came across, and a homework assignment I had to do several years ago, suggested that the reason we can skate on ice is the peculiar $p(T)$-curve of the ice-water boundary. The reasoning is that due to the high pressure the skates put on the ice, it will melt at temperaturs below $273 K$ and th... | 22 |
<p>Does anyone know how the acuity of your vision translates to a difference in limiting magnitude?</p>
<p>e.g., the kind of answer I'm looking for would be
"For each factor of 2 improvement in your vision (20/80 to 20/40, 20/40 to 20/20, 20/20 to 20/10, etc., your personal limiting magnitude for point sources increas... | 6,494 |
<p>How do scientists calculate that density? What data do they have to calculate that?</p> | 6,495 |
<p>The nebulae we see in the night sky are forming new stars.</p>
<p>The stars are eating up the nebulae and there is no obvious process in which those nebulae are being created to compensate for that.</p>
<p>Shouldn't the universe have run out of those nebulae a long time ago?</p> | 6,496 |
<p>I was reading the article <em><a href="http://www.bbc.co.uk/news/science-environment-14372708">Oxygen finally spotted in space</a></em> today in which it stated </p>
<blockquote>
<p>Oxygen is the third most abundant element in the cosmos, after
hydrogen and helium.</p>
</blockquote>
<p>Why would <a href="http:... | 6,497 |
<p>Neutrons have a measureable magnetic dipole momentum from their intrinsic spin. Is it possible to slow down and catch the neutron by imposing a force by an inhomogeneous magnetic field. I think the force the neutron experiences in a magnetic field is
\begin{align}
\bar{F} = \bar{\nabla}(\bar{m}\cdot\bar{B}).
\end{al... | 6,498 |
<p>I am having trouble in understanding why in $Z_2$ topological insulators odd number of Kramers' pairs on one edge are protected by time reversal symmetry against elastic backscattering while even number of such Kramers' pairs are not. I am aware of the argument saying time reversal invariant perturbation can only co... | 6,499 |
<p>What's the entropy of the universe today? How does one go about calculating this? I've heard the statement that black holes account for the bulk of the entropy in the universe today, but don't know why this would be true or the relationship between black holes and entropy.</p> | 568 |
<p>A few years ago in an astronomy course, we calculated some (transverse?) velocity of a moving object and got super luminal results. The answer was apparent and not physical velocity of the object. Hence no problem. But at the moment, I don't recall the solution to this apparent issue. Anyone? </p> | 6,500 |
<p>If time in systems moving with different speed goes differently, does speed of entropy change differ in these systems?
(is "speed of entropy change" a valid term? can we compare them?)</p> | 6,501 |
<p>What is the parity eigenvalue of the $W^{\pm}$ boson, or is it even an eigenstate? I have not found any source that discusses this. I have seen some lists of particles with their parity eigenvalues, but the $W^{\pm}$ and $Z^{0}$ bosons are always left out. </p> | 6,502 |
<p>I want to know what mathematical theories I should be aware of for a deep understanding of the standard particles model.</p> | 223 |
<p>Is there a particular reason, why the <a href="http://icecube.wisc.edu/" rel="nofollow">Icecube experiment</a> has been installed at the South pole and not at the North pole?</p> | 6,503 |
<p>If I have a parallel circuit with two resistors ($R_1=48 \Omega$ and $R_2=16 \Omega$) - and $R_1$ has a $0.1 A$ current running through, is it possible to calculate the current through $R_2$ without having the voltage given, an if so, how?</p> | 6,504 |
<p>I understand normal force to be the perpendicular force to a surface of contact. However, I have come across a problem which has caused me to rethink this. </p>
<p>My initial understanding of force is demonstrated by the following diagram of an object sliding down an inclined plane.</p>
<p><img src="http://i.stack... | 6,505 |
<p>Ok so I am an A2 physics student, and for one of my pieces of coursework I conducted a practical investigation, my topic being the factors affecting the period and swing of a bifilar pendulum.</p>
<p>The only useful information I was able to find on the topic was here: <a href="http://voyager.egglescliffe.org.uk/ph... | 6,506 |
<p>This capacitance contain 4 dielectric as shown in the figure dielectric 1 in half sphere and 2,3 in for 1/4 of the sphere and the fourth one in the last 1/4 of the sphere as shown and I want to find total capacitance.
i think that 2nd dielectric parallel with potion of 1st and portion of 4th then this group series w... | 6,507 |
<blockquote>
<p>A linearly polarized plane wave at 100 MHz is propagating in the $z$ direction. The electric field vector makes an angle of 30° with the $x$-axis. Its peaks amplitude is measured to be $2.0\:\mathrm{ V m}^{-1}$. Write down equations for the electric field and magnetic fields components of the wave as ... | 6,508 |
<blockquote>
<p>An object falls from a height $h$ above water through air with negligible drag. In the water, the upward buoyancy exactly balances the downward gravitation force. The only remaining force on the body in the water is a drag force with magnitude $cv^2$ per unit mass, $c$ is a constant, and $v$ is the ve... | 6,509 |
<p>The situation looks as follows:
<img src="https://dl.dropboxusercontent.com/u/76821907/incline.png" alt="situation"></p>
<p>The incline is moving rightwards with a constant acceleration<br>
<img src="https://dl.dropboxusercontent.com/u/76821907/latex1.png" alt="a=g"></p>
<p>The forces on the picture are:
mg - weig... | 6,510 |
<p>Forgive me if this is a newb question but I am not a trained scientist, much less a physicist. I'm just curious and would like to know if there's a unit to measure impact force.</p>
<p>I know the newton is the amount of force required to accelerate a mass of one kg at a rate of 1m/s^2 but what about the impact itse... | 6,511 |
<p>In Perkin's book Particle Astrophysics (page 144): I do not understand how one comes to the following expression (the second equality with $r$) for the Helium mass fraction due to the Big Bang Nucleosynthesis:</p>
<p>$$Y= \frac{4N_\text{He}}{4N_\text{He}+N_\text{H}}= \frac{2r}{1+r} $$
where $r=N_\text{n}/N_\text{p}... | 6,512 |
<p>As discussed <a href="http://www.math.poly.edu/courses/projective_geometry/chapter_three/node1.html" rel="nofollow">here</a> the complex projective space $\mathbb{C}P^n$ is the set of all lines on $\mathbb{C}^n$ passing through the origin. It would seem natural to assume that any $\mathbb{C}P^n$ can be viewed as a ... | 6,513 |
<p>I have a little problem with the potential energy of a spring... I hope you can help me!</p>
<p>I have two coupled pendula, given by two masses $m$ fixed to two rigid bars (that haven't any mass) and with length $L$ and $2L$. The two bars are at the distance $d$. The masses are connected each other with a spring of... | 6,514 |
<p>I am reading the paper "Bosonization in a Two-Dimensional Riemann-Cartan Geometry", Il Nuovo Cimento B Series 11
11 Marzo 1987, Volume 98, Issue 1, pp 25-36, <a href="http://link.springer.com/article/10.1007%2FBF02721455" rel="nofollow">http://link.springer.com/article/10.1007%2FBF02721455</a></p>
<p>Equation 4.8' ... | 6,515 |
<p>For resonance to occur, is it true that the force lags behind the motion by $\pi/2$? I saw some notes written that the motion lags behind the force by $\pi/2$ which makes no sense to me.
As I watched many videos and I worked out the motion, it always happens before the force pushes.
E.g. if the force is $F=\cos\omeg... | 224 |
<p>As we know that the Schrödinger equation presents basis of Quantum Mechanics and analogy with Newton second law in Classical Mechanics, I thought that relativistic interpretation of Schrödinger equation can make general relativity and quantum mechanics closer</p>
<p>$$ \frac {1}{c^2} \frac{\partial^2}{\partial t^2}... | 6,516 |
<p>Just a curious question, do astrophysicist use the SI units, for example in this equation, </p>
<p><img src="http://i.stack.imgur.com/Mj11w.png" alt="enter image description here"> </p>
<p>$r = 5pc$, will this be converted to meters?
And what does this $\nu$ stand for? </p> | 6,517 |
<p>Obviusly a controlled-not gate is possible, is a not-controlled gate possible?</p>
<p>I need a gate to flip the first qbit and leave the second unchanged, but in literature I have never seen such a gate.</p>
<p>Would it look like $$
\left(\begin{matrix}
1 & 0 & 0 &0 \\
0 &1& 0 & 0 \\
... | 6,518 |
<p>In QM, the wave function (in the Copenhagen interpretation) is not an actual physical wave but a device to derive probabilities about the outcomes of experiments. The wave function encodes all the information about the system we want to derive predictions for. Predictions are about future measurements. Once the mea... | 6,519 |
<p>Bacteriochlorophyll (BChl) are pigments that occur in the photosynthetic mechanisms of bacteria. I am studying some papers on the excitonic properties of BChl's, and the term $Q_y$ transition comes up a lot, but I haven not found any explanation of its meaning. </p>
<p>Can someone explain to me the meaning of this ... | 6,520 |
<p>On <a href="http://quantummechanics.ucsd.edu/ph130a/130_notes/node82.html" rel="nofollow">this page</a> right at the top they mention two sets of fourier transform. First set is connection between $x$ (position) and $k$ (wave vector) space: </p>
<p>$$
\begin{split}
f(x) &= \frac{1}{\sqrt{2\pi}} \int\limits_{-\i... | 6,521 |
<p>I was trying to naively draw a parallel between special relativity and the Heisenberg uncertainty principle. I try to understand uncertainty principle as a consequence of 4-position and 4-momentum being conjugate variables in phase space, and this arises from a Lagrangian that looks like this: $p_\mu dx^\mu$. If in ... | 6,522 |
<p>I am trying to understand <strong>the Bernoulli's theorem:</strong></p>
<ul>
<li><strong>$\frac{p}{\rho}+\frac{1}{2}u^2+\phi$ is a constant along a streamline</strong></li>
</ul>
<p>I got that:</p>
<p>$\frac{\partial u}{\partial t}$ + ($\nabla \times u)\times u$ = $-\nabla(\frac{p}{\rho}+\frac{1}{2}u^2+\phi)$</p>... | 6,523 |
<p><a href="http://en.wikipedia.org/wiki/Dislocation" rel="nofollow">Dislocation</a> (like <a href="http://en.wikipedia.org/wiki/Dislocation#Screw_dislocations" rel="nofollow">screw</a> or <a href="http://en.wikipedia.org/wiki/Dislocation#Edge_dislocations" rel="nofollow">edge</a> dislocation) is not a 'real' thing, wh... | 6,524 |
<p>I know thought that a crystal, if annealed for long enough at high enough temperatures, will "shed" its higher index (higher energy) planes, leaving only its most stable form. This, I wrongfully assumed, was the shape of its primitive cell. Some crystals however, notably pyrite, do tend to take the shape of their pr... | 6,525 |
<p>I have looked at some of <a href="http://www.staff.science.uu.nl/~hooft101/" rel="nofollow">'t Hooft</a>'s recent <a href="http://www.staff.science.uu.nl/~hooft101/gthpub.html" rel="nofollow">papers</a> and, unfortunately, they are well beyond my current level of comprehension. The same holds for the discussions tha... | 6,526 |
<p>Voltage is the work done per unit charge. Given by:</p>
<p>V = W/q</p>
<p>Electron volt is the maximum kinetic energy gained by the electron in falling through a potential difference of 1 volt. Given by:</p>
<p>K.E (max) = eV</p>
<p>When there is a potential difference (voltage) of 10V between two points, it mea... | 6,527 |
<p>I have the following problem for an astrophysics course:</p>
<blockquote>
<p><em>A star is seen through a rather dusty region of space has its
brightness dimmed by +1 magnitude/kpc, which makes it seem further
away than it actually is. If the observed apparent magnitude of the
star is $m_v = +4.0$ and absol... | 6,528 |
<p>How can one prove the Bianchi identity of a non-Abelian gauge theory? i.e.
$$
\epsilon_{\mu \nu \lambda \sigma}(D_{\nu}F_{\lambda \sigma})^a=0
$$</p> | 6,529 |
<p><a href="http://en.wikipedia.org/wiki/Holeum" rel="nofollow">Here</a> is the wikipedia article. The basic idea is that the primordial density of microscopic black holes was high enough that many were able to form stable bound states before decaying through Hawking radiation (similarly to how unstable neutrons were a... | 6,530 |
<p>You often hear intergalactic space is an example for a very good vacuum. But how vacuos is space between galaxy clusters and inside a huge void structure? Are there papers quoting a measurement/approximation method (building the difference of a very near known and far away similar spectral source)? Are the rest part... | 262 |
<p><img src="http://i.stack.imgur.com/0nuvB.jpg" alt="enter image description here"></p>
<p>In order to workout the method for establishing the formula of thin lens, my teacher says that the optical path is:
$PA + AQ = PS_1 + nS_1S_2 + S_2Q$ ($n$ is the refractive index of the lens)<br>
Why is she multiplying ... | 6,531 |
<p>Why do we have to divide uncertainty of the measurement by $\sqrt{3}$?</p>
<p>For example we have the uncertainty of the measurement with a ruler being the smallest scale of 0.01cm, and it is not our uncertainty but we first divide it and so it makes our final uncertainty value.</p>
<p>Why is that this way?</p> | 6,532 |
<p>In recent exoplanet meeting <a href="http://seagerexoplanets.mit.edu/next40years.htm" rel="nofollow">The Next 40 Years of Exoplanets</a>, it was mentioned a few times that the field/topic is becoming saturated.</p>
<p>In what ways is it becoming saturated, and can you see the effect of this in the quality of papers... | 6,533 |
<p>From the Apollo missions we know that the moon is covered with dust. Where does it come from? Is it from the erosion of the moon rock? By what? Or by accretion of dust from space? Which comes from where?</p> | 6,534 |
<p>Suppose a police car is standing by a wall. The siren light is rotating and it will hit the wall and reflect back to the car. Does the reflected light show a Doppler effect? </p> | 6,535 |
<p>What is the most precise data for neutron-antineutron production by one photon (hitting a target in the laboratory system)?</p>
<p>and/or</p>
<p>What is the most precise data for neutron-antineutron
annihilation to two photons?
Is this data available online?</p> | 6,536 |
<p>One of the key datasets of the <a href="http://arxiv.org/abs/1403.3985" rel="nofollow">recent BICEP2 results</a> is the B mode power spectrum shown below. The existence of these B modes implies the existence of gravitational waves prior to inflation. </p>
<p>My question is: what is the relationship between the ... | 6,537 |
<p>Could it be said (as my question implies) that elementary particles (can) exist in three quite different states: wave, point-particle and superposition?</p>
<p>So, a wave or a point-particle could be 2 manifestations of an elementary particle in "our-macrocosmos dimension" and a superposition would be a third state... | 6,538 |
<p>I am working on the following physics problem and have run into some trouble</p>
<p><img src="http://i.stack.imgur.com/Qcwhu.png" alt="enter image description here"></p>
<blockquote>
<p>The figure above shows particles $1$ and $2$, each of mass $m$, attached to the ends of a rigid massless rod of length $L_1 + L... | 6,539 |
<p>I want to combine three spin half particles and this is what I have so far.</p>
<p>I used the lowering operator $J_{-}$ on the top states and found the following states fine:</p>
<p>$$|\frac{3}{2},\frac{3}{2}\rangle , |\frac{3}{2},\frac{1}{2}\rangle , |\frac{3}{2},0\rangle , |\frac{3}{2},-\frac{1}{2}\rangle , |\fr... | 6,540 |
<p>I'm watching a lot of basketball <a href="http://www.ncaa.com/march-madness" rel="nofollow">this month</a>. A common event is the ball going part way into the hoop and then coming out again. Announcers sometimes claim that the ball was "halfway through" when it rims out. Thinking about it, with enough rotation and f... | 6,541 |
<p>As from the title, I'm not too sure how they are related. Definition is that <a href="http://en.wikipedia.org/wiki/Streamlines,_streaklines,_and_pathlines" rel="nofollow">streamlines</a> are instantaneously tangential to the velocity vector of the field. Why would a streamline that shows direction be a tangent to th... | 6,542 |
<p>There are two identical LC oscillators with electronic counters attached indicating how many times they have oscillated (from the time they are turned on).
They are turned on simultaneously and one is kept on earth and other one is hurled to outer space at very large speeds on a rocket and brought back to earth afte... | 6,543 |
<p>While discussing this question (<a href="http://physics.stackexchange.com/q/82296/">Does light have an unending journey?</a>) I stumbled on the fact that light's speed is constant only in inertial frame.</p>
<p>What I happened to do was add up the expansion of universe to the theory. It goes as follows: </p>
<p>Su... | 6,544 |
<p>I have somewhat of an understanding for other physical quantities, but as far as <a href="http://en.wikipedia.org/wiki/Entropy" rel="nofollow">entropy</a> goes I only know it to be "disorder". Why is the change in entropy formula an appropriate/useful definition, moreover, why is the equation for entropy an appropri... | 6,545 |
<p>The Earth rotates about it's own axis. Do the geomagnetic field lines rotate due to this rotation or not? </p> | 6,546 |
<p>How did <a href="http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion" rel="nofollow">Newton's third law</a> came into being? Was it his original finding like the second law? Or was it more of a restatement of someone else like the 1st one coming from Galileo? In either case what initiated the thought of what is n... | 6,547 |
<p>According to the 2nd law of thermodynamics, no system can be a 100% efficient. Looking at the universe as it's own system, is it an exception to the rule (a system that doesn't lose any energy)? If not, are there any theories that suggest where the energy go?</p> | 6,548 |
<p>Is there an unit of color charge? I haven't found it, so I suppose that it doesn't exist, if this is right, why? Isn't it supposed that every measurable quantity can be expressed in terms of base quantities? What about flavour charge?</p> | 6,549 |
<p>Euteictic freeze crystallization is a method where an electrolytic solution is cooled and separated into a stream of (relativly) clean, pure ice and a salty brine. I know anectdotally of wine concentrates that where made similiar. Now I wonder wether a suspension of solids can be separated in a similiar way, and if ... | 6,550 |
<p>I was solving a question about inclined planes, and it got me thinking:</p>
<p>Imagine a scenario where, an object is on an inclined plane and the inclined plane is on a frictionless surface, and is itself frictionless. </p>
<p>Now, if the mass of the object is comparative, or maybe, even more than the mass of the... | 6,551 |
<p>I apologize if this question is trivial, but I am new to physics and am struggling with some of the basic concepts.</p>
<p>Working in $\mathbb{R}^2$ with standard coordinates $(x,y)$, suppose we have a particle of mass $m$ moving on a curve $(x(t),y(t))\in\mathbb{R}^2$. It's tangent vector (velocity vector) is $$x^... | 6,552 |
<p>I hope this isn't a dumb question, but...</p>
<p>If we have two fixed sine waves, both of which have a frequency range of +1 to -1, with a ratio between the waves of wave(1):3 to wave(2): 1, what does the Schrodinger equation tell us (if anything) about the relationship between the waves?</p>
<p>Equally, if the wa... | 6,553 |
<p>SI system uses all (that I know) measurement basic units as 1 (single) instance: meter, second, ampere, etc, <strong>except the KILOgram</strong>. It already defined with 1000 multiplier (kilo).</p>
<p>It prevents from using usual multiplier prefixes: <em>mega, giga, tera</em>, ... Though we sometimes use miligrams... | 6,554 |
<p>Is temperature solely a function of a kinetic energy? If a solid and a gas are at thermal equilibrium at a temperature of 20 degrees Celsius, the solid has much less kinetic energy than the gas. How can the temperatures of both be the same? What is keeping the solid at the same temperature as the gas?</p> | 6,555 |
<p>I am doing a project with some small miniature incandescent light bulbs (like a <a href="http://vcclite.com/_pdf/T-1%203_4%20Midget%20Flange%20Base.pdf" rel="nofollow">CM7333</a>).</p>
<p>Sorry for not providing more links, the system will only allow 2.</p>
<p>The power source is a <a href="http://www.datasheets.p... | 6,556 |
<p>I do not understand this because angular momentum is $L=I\omega$ ($I$ is moment of inertia;$\omega$ is angular velocity) but it I have also seen equations where $L= rmv\sin(x)$. I do not understand how these are related, could someone please explain the connection?</p> | 6,557 |
<p>If I were to get a conductor e.g. a piece of copper wire or aluminium and connect it to one pole of a battery (let's take the positive pole for example), will electrons be removed from the conductor forming Cu or Al ions? Or does the flow only start when the circuit is completed?</p>
<p>I think as soon as a pole is... | 6,558 |
<p>Is putting a balloon that is charged up against a wall and having it stick polarization AND charging by temporary induction, or just polarization?</p> | 6,559 |
<p>Is it really impossible to calculate in advance the result of throwing dice? After all, the physics of dice throwing is in the world of classical mechanics, rather than quantum mechanics.</p> | 6,560 |
<p>The sphere has radius $R$ and is missing its "pole" - meaning that in the area $\theta\leq\alpha$ there is nothing. The object has a homogenous charge density $\sigma=\frac{Q}{\pi R^2}$</p>
<p>I'm trying to derive what the field inside and outside is. It should be a Legendre polynomials excercise. I know this is an... | 6,561 |
<p>The dimensions of circulation $\int_C \vec{v}\cdot d\vec{r}$ seem strange, but if you include
(even a constant) density $\rho$, then $\int_C \rho\vec{v}\cdot d\vec{r}$ has dimensions
the same as action/volume. Is there any significance to that? Is there any heuristic way to
think about circulation which helps under... | 6,562 |
<p>I used to live in Boston. Near my complex, there was an apartment complex with lots of our friends. Anyways, that place had faulty heating most of the time; mainly in the corridors. They were pretty stuffy.</p>
<p>One thing I'd noticed was that in our complex, static shocks were common but not too strong. Touching ... | 6,563 |
<p>I am just beginning to learn magnetism and my book used two ways to define the force caused by the magnetic field, brushing over the latter.
The first:</p>
<p>$$F = q v B \sin (\theta).$$</p>
<p>And:</p>
<p>$$\vec{F} = q(\vec{v} \times \vec{B})$$</p>
<p>where the $ \times $ is the cross product. After looking... | 6,564 |
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