question stringlengths 37 38.8k | group_id int64 0 74.5k |
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<p>A molecule consists of two atoms whose centers are located at $\mathbf{r}_1$ and $\mathbf{r}_2$ respectively. The atoms are connected by a bond that can be approximated by a
harmonic spring, so that its energy as a function of the separation between the atoms $\mathbf{r}=\mathbf{r}_1-\mathbf{r}_2$
is $$U(r) = (akTr^... | 4,551 |
<p>I'm having some trouble with successfully working out a rotation about the $z$-axis on the <a href="http://en.wikipedia.org/wiki/Bloch_sphere" rel="nofollow">Bloch sphere</a>.
Now, I know how this is performed, in principle.
A rotation of the Bloch-sphere around an axis $\boldsymbol n$ by an angle $\theta$ is give... | 4,552 |
<p>I am considering the cathode ray tube of the set up, when the cathode rays were discovered</p>
<p>Voltage = Very High<br />
Gas = any<br />
Atmospheric Pressure = We change</p>
<p>(In the following example i am just changing the atmospheric pressure everything else is kept same)</p>
<p>At <br />
1 atmospheric pre... | 4,553 |
<p>On pp 103 - 105 of <em>The Character of Physical Law</em>, Feynman draws this diagram to demonstrate that invariance under spatial translation leads to conservation of momentum:</p>
<p><img src="http://i.stack.imgur.com/BrYgE.jpg" alt="enter image description here"></p>
<p>To paraphrase Feynman's argument (if I un... | 4,554 |
<p>Imagine a vertical pipe (both ends opened) in the water. Drop several ping-pong balls into pipe and cover them with a cylinder. When you have enough balls, the cylinder will float. Now start adding weight into the top of a cylinder, and simultaneously start adding ping-pong balls via the bottom of pipe, to compensat... | 4,555 |
<p>My 8yo son is in the Cub Scouts.</p>
<p>He has a pinewood derby coming up next month and I would like to take this project and turn it into a fun, physics lesson for him. </p>
<p>For those not familiar, a pinewood derby is where you shape a block of wood into a car (or truck, or where ever your imagination leads ... | 4,556 |
<p>When <code>taxpayers</code> pay <code>money</code> for expensive research (irrespective of the <code>partition-function</code> wheither a few projects worth <code>megabucks</code> [<code>M$</code>] or many smaller cheaper experiments), should the <code>raw data</code>/<code>designs</code>/... that result from it be ... | 4,557 |
<p>A <a href="http://en.wikipedia.org/wiki/Vortex_tube">Vortex Tube</a> takes a pressurized input stream, most typically of a gas, and creates two output streams with a temperature differential. <a href="http://www.exair.com/Cultures/en-US/Primary+Navigation/Products/Vortex+Tubes+and+Spot+Cooling/Vortex+Tubes/A+Phenome... | 316 |
<p>Ive read a few courses on <strong>statistical mechanics</strong>, and while their textual explanations and example choices differ, the flow of information from microscopy to macroscopy seems the same, and reading between the lines you can see some mathematical construct. Has statistical mechanics been formalized in ... | 4,558 |
<p>Please move this if it's not in the right location.</p>
<p>I'm looking for the name of a device that I frequently see in many scenarios, specifically that of an office/library which can be described as having multiple rings that rotate in various directions. I was thinking it was a gyroscope or perhaps a celestial ... | 4,559 |
<p>Suppose we view fluids classically, i.e., as a collection of molecules (with some finite size) interacting via e&m and gravitational forces. Presumably we model fluids as continuous objects that satisfy some differential equation. What mathematical result says that modeling fluids as continuous objects can accur... | 187 |
<blockquote>
<p>If it takes work W to stretch a Hooke’s-law spring (F = kx) a distance d from its unstressed length, determine the extra work required to stretch it an additional distance d (Hint: draw a graph and give answer in terms of W!).</p>
</blockquote>
<p>I don't understand why the answer is not 2W since For... | 4,560 |
<p>Is it possible to reclaim nuclear waste from commercial reactors for useful purposes, if not necessarily energy production?</p> | 4,561 |
<p>Case 1: two people wake up in spaceships accelerating at 1g. They can measure or observe anything inside the room but not outside. They couldn't determine if they were on a spaceship or on earth. If they ever communicated in the future they would be the same age. Is this correct?</p>
<p>Case 2: one person wake... | 4,562 |
<p>I just want a book on classical mechanics that covers the same ground as Goldstein's book but is more on the line of DJ Griffiths's Classical Electrodynamics. I mean less formal and more conversational. </p> | 98 |
<p>In QFT we associate to each Gauge theory a continuous group of local transformations (a Gauge group), and then we require\define fermion fields to be irreducible representations belonging to the fundamental representation of this Gauge group.</p>
<ol>
<li><p>What is the <a href="http://en.wikipedia.org/wiki/Fundam... | 4,563 |
<p>How does one see it as obvious that</p>
<p>$$\int_S \frac{\partial A_i}{\partial x^j} dS^{ji} = \int_S\frac{1}{2}(\frac{\partial A_j}{\partial x^i} - \frac{\partial A_i}{\partial x^j})dS^{ij}$$</p>
<p>where $d S^{ij} = dx^i dx^{j*} - dx^j dx^{i*} $</p>
<p>From <a href="http://books.google.ie/books?id=X18PF4oKyr... | 4,564 |
<p>Suppose you have an 1-dimensional system with a charge distribution $\rho(x)$ (not given) moving with an speed $v(x)$ (not given), calculate the potential $\phi(x)$ and the charge distribution $\rho(x)$ in the quasistatic limit $\frac{d}{dt}=0$. </p>
<p>Hints:</p>
<p>$\frac{d^{2} \phi}{dx^{2}}=-\rho/ \varepsilon_... | 4,565 |
<p>Photons have no charge. Light is a form of electromagnetic energy.</p>
<p>All spectroscopic effects (to my knowledge) are due to changes in electron state, induced either through an interior or exterior EM (Electro-Magnetic) field. EM forces may affect that state, which in turn affects the light emitted during the... | 4,566 |
<p>For years I have been very fascinated by the "mystery" aspect of gravity. Functionally, we understand it perfectly for our all applications, but in my (limited to undergrad General Physics 3 quarters) understanding, we don't know WHY it exists or HOW the "pull" works. </p>
<p>I'm very sorry for what is surely trite... | 4,567 |
<p>Depending on the theories, the center of our galaxy is a super massive black hole, this is easy to accept as a truth, but what I couldn't simply devour is how the solar system is orbiting around it while not getting absorbed to the inside ? It's simple to understand how earth orbits the sun, but the black hole is so... | 4,568 |
<p>Suppose I have plenty of food I want to heat (which will provide load) in the microwave, and one item I don't want to heat. What properties would make a material a a good shield, to reduce or prevent heating of that item? I know metal can work as a barrier in the form of a Faraday cage, but that there are also poten... | 4,569 |
<p>I'm trying to introduce myself to QFT following <a href="http://www.damtp.cam.ac.uk/user/tong/qft.html" rel="nofollow">these lectures</a> by David Tong. I've started with lecture 1 (Classical Field Theory) and I'm trying to prove that under an infinitesimal Lorentz transformation of the form</p>
<p>$$\tag{1.49} {\L... | 4,570 |
<p>In proving that the action $$S\equiv \int^{t_2}_{t_1}L(x, x',t)dt$$ has a has a stationary point $x_0$ that satisfies the following:
$$\frac{d}{dt}(\frac{\partial L}{\partial x'_0})=\frac{\partial L}{\partial x_0}$$
My textbook finds the action of $$x_a(t)\equiv x_0(t)+a\beta (t)$$ differentiated with respect a to t... | 4,571 |
<p>I am looking for a device to provide variable excitation voltage (30VDC to 200VDC) to a Transducer for a variable time (10 to 20 milliseconds).</p>
<p>Can someone please advise how I could achieve this using an off the shelf product? </p> | 4,572 |
<p>I know that if the Helmholtz free energy, $A$, is expressed as a function $A\sim A(N,V,T)$, then this function contains all thermodynamic information about the system. For instance, the pressure of the system is given by:</p>
<p>$$P(N,V,T) = -\frac{\partial A}{\partial V}\Bigg|_{n,T}$$</p>
<p>Indeed, if we imagin... | 4,573 |
<p>Eq (1.137) in Negele and Orland gives the following identity for a normal-ordered operator $A(a_i^\dagger,a_i)$:</p>
<p>$$\langle \phi|A(a_i^\dagger,a_i)|\phi'\rangle=A(\phi_i^*,\phi'_i)e^{\sum \phi_i^*\phi'_i}$$</p>
<p>For the coherent (boson) states $|\phi\rangle=e^{\sum\phi_ia^\dagger_i}|0\rangle $. When I try ... | 4,574 |
<p>Can we generate a pulse , transmit it and after that can we record it's response time ?</p>
<p>I am curious because I want to know that is it possible to make a mapping device (like SLAM) which uses this technique.
I have done a little search but didn't get the satisfying result .
If any one has any idea about thi... | 4,575 |
<p>In the book "A Briefer History of Time" Stephen Hawking wrote:</p>
<blockquote>
<p>The unpredictable, random element comes in only when we try to
interpret the wave in terms of the positions and velocities of
particles. But maybe that is our mistake: maybe there are no particle
positions and velocities, but... | 4,576 |
<p>What happens if I charged a capacitor then i touch the 2 poles in same time?</p> | 4,577 |
<p>This question is a follow-up to <a href="http://physics.stackexchange.com/users/2190/david-bar-moshe">David Bar Moshe</a>'s answer to my earlier question on the <a href="http://physics.stackexchange.com/questions/34990/aharonov-bohm-effect-and-flux-quantization-in-superconductors">Aharonov-Bohm effect and flux-quant... | 4,578 |
<p>I would like to point to the beautiful section 4.3 (page 42) of <a href="http://www.people.fas.harvard.edu/~xiyin/253b_Lectures.pdf">these lecture notes.</a> I think this is the most educative exposition I have ever seen anywhere about Yang-Mill's beta function. What I love best about it is that it does it without ... | 4,579 |
<p>I've looked in and out the forum, and found no precise definition of the meaning of <a href="http://en.wikipedia.org/wiki/Fine-tuning" rel="nofollow">fine-tuning</a> in physics.</p>
<p><strong>QUESTION</strong></p>
<p>Is it possible to give a precise definition of fine-tuning?</p>
<p>Of course, I guess most of us... | 4,580 |
<p>I've come across a problem with finding the energy stored in time/frequency electric field. In space/time we have (taking $\epsilon = 1$)</p>
<p>$$ Energy = \frac{1}{2} \int_V |\mathbf{E}(\mathbf{x},t)|^2 \;d^3x $$ </p>
<p>But, I presume that the formula is different for a frequency-dependent electric field. I've ... | 4,581 |
<p>I was watching a youtube video the other day where an economist said that he challenged his physics professor on this question back when he was in school. His professor said each scenario is the same, while he said that they are different, and he said he supplied a proof showing otherwise.</p>
<p>He didn't say whet... | 58 |
<p>Are all <a href="http://en.wikipedia.org/wiki/Wave" rel="nofollow">waves</a> in the universe the same as <a href="http://en.wikipedia.org/wiki/Electromagnetic_waves" rel="nofollow">electromagnetic waves</a>?</p>
<p>Basically, my question arises from an equation I found in my chemistry textbook:</p>
<p>$$\lambda \n... | 4,582 |
<p>I'm creating a simple astronomy simulator that should use Newtonian physics to simulate movement of plants in a system (or any objects, for that matter). All the bodies are circles in an Euclidean plane, that have properties such as position, velocity, mass, radius and the resultant force.</p>
<p>I want to update t... | 4,583 |
<p>We know that space-time dimensions are 3+1 macroscopically, but what if 2+2?
Obviously it is tough to imagine two time dimensions, but mathematically we can always imagine as either having two parameters $t_1$ and $t_2$ or else in Lorentz matrix
$$\eta_{00} = \eta_{11} = -1$$ and, $$\eta_{22} = \eta_{33} = 1.$$</p>... | 4,584 |
<p>Suppose there are two electrons in an atom with $s_1 = \frac{1}{2}$, $l_1 = 1$ and $s_2 = \frac{1}{2}$, $l_2 = 1$. Hence the total $S$ (of the atom) may be +1 or 0. And total $L$ is either $+2$, $+1$ or $0$.</p>
<p>Now If we consider </p>
<p>$$\begin{align}
S=1,L=2 &\to 2S+1=3; J=3,2,1\\
S=0,L=2 &\to 2S+1=... | 4,585 |
<p>The question I have in mind is: <strong>If we place a conductor (arbitrary shape) of total charge zero in a uniform external electric field $\textbf{E}_0$, does it experience any net force? Why (not)?</strong></p>
<p>Now I will discuss the context of the question. I am working on Griffiths <em>Introduction to Elect... | 4,586 |
<p><a href="http://physics.stackexchange.com/q/27939/2451">Here</a> and <a href="http://physics.stackexchange.com/q/28181/2451">here</a> it states that water is at its highest density around $4^\circ$ Celsius. I know very little physics and a Google search has left me without an answer. I am teaching an <a href="http:/... | 4,587 |
<blockquote>
<p>I have a pot with water of mass $m$ and it is heated by a stove
element of temperature $T_E$ and with a surface area of $A$. The
water starts at temperature $T_W > 0^\circ\, C$.</p>
<p>How long would it take to heat up this water to a final temperature of
$T_F$ ($T_W<T_F < 100^\ci... | 4,588 |
<p>$$E_{\mathrm{ms}} = \frac{1}{2}\mu_0 \int_V \mathbf{M} \cdot \mathbf{H}_{\mathrm{ms}} d^3 r$$</p>
<p>I can't understand this formula, what is the magnetostatic stored potential energy?! What does it show?
Does it explain anything relative to magnetization?</p> | 4,589 |
<p>I try to understand constructing of Hamiltonian mechanics with constraints. I decided to start with the simple case: free relativistic particle. I've constructed hamiltonian with constraint:</p>
<p>$$S=-m\int d\tau \sqrt{\dot x_{\nu}\dot x^{\nu}}$$</p>
<p>$\phi=p_{\mu}p^{\mu}-m^2=0$ $-$ <a href="http://en.wikiped... | 4,590 |
<p>Let's have potential
$$
U(r) = -U_{0}e^{-\frac{r}{a}}.
$$
I need to find energy levels for particles moving in this field (for an arbitrary values of orbital number $l$). This task isn't exactly solvable, so I need some method which can help to find approximate energy levels.</p>
<p>What to do?</p>
<p>I reduced th... | 4,591 |
<p>With relativistic aberration, a sky full of stars gets concentrated in the direction of motion. As a rough measure of the degree of concentration, one could use the radius of a small circle, centered on the direction of motion, which contains the objects which, when you are at rest, are in half the sky (if you take ... | 4,592 |
<p>I would like to buy a good book on Variational Calculus. Most of the books that I find seem to be rather formal in a mathematical sense, which is not necessarily bad, but makes the studying a bit cumbersome.</p>
<p>Could you provide me with advice on a good variational calculus books which focuses on physics proble... | 150 |
<p>The equation of motion for the harmonic oscillator (mass on spring model)</p>
<p>$$\frac{d^2x}{dt^2} + \omega_0^2 x = 0$$</p>
<p>with $\omega_0^2 = D/m$, $D$ and $m$ being the force constant of the spring and the mass, has the solution</p>
<p>$$x=ce^{\lambda t}$$</p>
<p>where $c$ and $\lambda$ are a constant and... | 4,593 |
<p>We know that in an isolated system, the density matrix is the microcanonical distribution matrix. That this the possibility for all the states with energy in a certain interval is a constant?
But how can I deduce this from the postulate of equal probability? </p> | 4,594 |
<p>I am trying to the calculate the link budget for link between a ground station on Earth (with a particular latitude and longitude) and a rover at a particular location on the surface of Mars, either directly or through a satellite on Mars. Now, if I need to determine the link availability between the rover and the g... | 4,595 |
<p>When working with Bose-Einstein condensates trapped in potentials, how can one tell what the density of state of a system of identical bosons given the Hamiltonian, $H$? (I have been told that it is possible.)</p>
<p>Suppose the Hamiltonian is some 2D harmonic oscillator -- so $$H=p^2/2m+(1/2)(a^2x^2+b^2y^2) \quad ... | 4,596 |
<p>I've been wondering exactly why the elements are distributed the way they are on Earth. The heavier elements have their origins in the centers of stars, or in supernovae. After the death of the stars, you end up with a dust cloud containing the heavier elements. Later, planets form out of these along with new stars.... | 4,597 |
<blockquote>
<p><em>A) Explain how Kepler's $2^{nd}$ law - "The radius vector from the Sun to a planet sweeps out equal areas in equal time intervals" - can be understood in terms of angular momentum conservation.</em></p>
</blockquote>
<p>I know that:</p>
<p>Angular momentum is conserved and therefore $\vec{L}=\ve... | 4,598 |
<p>Suppose there's some satellite orbiting the earth in circular motion. Suppose there's an asteroid that hits the satellite in the same direction as the instant velocity vector of the satellite. The collision causes the satellite to move faster. And here are my 2 questions:</p>
<p>1) Why will the satellite start movi... | 4,599 |
<p>This question is about cosmology and general relativity.</p>
<p>I understand the difference between the universe and the observable universe. What I am not really clear about is what is meant when I read that the universe is infinite.</p>
<ul>
<li>Does it have infinite mass or is it
dishomogeneous? </li>
<li>How c... | 922 |
<p>Here's something that I've found difficult to wrap my head around. The relationship between the Schwarzschild radius and mass is linear. It's generally known that if you take an object in the universe and squeeze it down to it's Schwarzschild radius, that radius will always be smaller than smaller than the original ... | 4,600 |
<p>I think we all heard general statements like "once big enough star burns out there is nothing to prevent the gravitational collapse ending in a black hole". But I can't remember even seeing the process described precisely.</p>
<p>Here's the deal: at first there is a nice object, a star. Stars can be nicely modeled ... | 4,601 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/14074/what-are-the-prerequisites-to-studying-general-relativity">What are the prerequisites to studying general relativity?</a> </p>
</blockquote>
<p>I'am 27 now and i have a burning desire to study math... | 108 |
<p>Consider an point particle moving on a frictionless semicircular hill (curve). The particle's initial kinetic energy is equal to the potential energy on the top of the hill, i.e it has the necessary energy to climb the hill. </p>
<p>Will it reach the top of the hill in infinite or finite time? </p>
<p>In my proof ... | 4,602 |
<p>I am making a comparation between the photon gas and the ideal classic gas for my Thermodynamics class. The photon gas is defined by the equations:</p>
<p>$$U=aVT^4 $$
$$P=\dfrac{1}{3}aT^4$$</p>
<p>I found this document: <a href="http://www.csupomona.edu/~hsleff/PhotonGasAJP.pdf" rel="nofollow">http://www.csupomon... | 4,603 |
<p>What is the molecular level reason behind the pattern (sine function) of the waves?</p>
<p><img src="http://i.stack.imgur.com/wAoQL.jpg" alt="enter image description here"></p> | 4,604 |
<p>Let a wire be shaped according to some even function $y=f(x)$, with $f'(0)=0$ and $f''(0)>0$, and let a bead of negligible size slide frictionlessly on the wire. Let the bead oscillate under the influence of gravity about $x=0$ with amplitude $A$ (i.e., between $x=-A$ and $x=+A$) and frequency $\omega... | 4,605 |
<p>When a ray of ordinary light is passed on the surface of the water the reflected light will be completely polarized( vibrations in one plane).</p>
<p>My question is what will be <strong>plane of vibration in the partially polarized light</strong> that undergoes refraction? <strong>How many planes of vibration</stro... | 4,606 |
<p>If a future astronaut travelled to Alpha Centauri at a significant percentage of light-speed?
Apart from increased blue shifted radiation from their direction of travel - how would they experience other cosmic radiation? </p>
<p>If the trip took a subject several times faster than an observer on earth. Would the as... | 4,607 |
<p>Wikipedia says:</p>
<blockquote>
<p>It is believed that, due to the extraordinarily small scale of the
universe at the time, quantum effects of gravity dominated physical
interactions.</p>
</blockquote>
<p>But I wonder whether there is any indication that the dimensions of the universe were small at the time... | 4,608 |
<p>The media are reporting the commercially sold 128-bit quantum computer from D-Wave</p>
<blockquote>
<p><a href="http://news.google.com/news?ned=us&hl=us&q=d-wave+quantum&cf=all&scoring=n">http://news.google.com/news?ned=us&hl=us&q=d-wave+quantum&cf=all&scoring=n</a></p>
</blockquot... | 528 |
<p>String theory - for example - requires extra spatial dimension. Say for example in 10 dimensional string theory, what theoretically prevents clustering of the extra 6 dimensions in 2 timeless 3 dimensional (infinite) spaces? </p> | 4,609 |
<p>Some time far into the future, humans have made the technology breakthroughs to construct decoherence-proof reversible quantum computers with quantum fault tolerance. They have also solved the hard AI problem. They program a quantum conscious being on such a computer and also a two state quantum system. The quantum ... | 4,610 |
<p>I can find equations to give the force of an electromagnet on a piece of iron when the iron touches the electromagnet. </p>
<p>But what about when the iron is some distance from the electromagnet? Presumably the force depends on the shape/size of the iron piece as well as the location of the piece away from the m... | 4,611 |
<p>How to estimate the amount of water condensing from air on a surface, given the air's temperature and relative humidity and how they change over time, the surface temperature, material's thermal properites, roughness and whatever else needs to be given about the air and surface?</p>
<p>For my purpose, we may assume... | 4,612 |
<p>Also the side question is how many Joules is one photon (any between 450-660nm).
Thank you</p>
<p>P.S. I am asking because I want to estimate how much thermal energy should be dissipated by LED when part of known energy is emitted as light.</p>
<p>P.S. Got an answer from Robert. Thank you.
So those 6500 Lumen 100W... | 4,613 |
<p>Cellular automata provide interesting models of physics: Google Scholar gives more than 25,000 results when searching for <a href="http://scholar.google.com/scholar?q=%22cellular+automata%22+physics&hl=en&btnG=Search&as_sdt=2001&as_sdtp=on">"cellular automata" physics</a>.</p>
<p>Google Scholar stil... | 4,614 |
<blockquote>
<p><strong>Possible Duplicates:</strong><br>
<a href="http://physics.stackexchange.com/questions/14973/what-would-be-the-immediate-effects-if-light-does-not-go-at-the-maximum-speed-pos">What would be the immediate effects if light does not go at the maximum speed possible?</a><br>
<a href="http://phy... | 83 |
<p>How does it make sense to vary the position and the velocity independently?</p>
<p><strong>Edit:</strong></p>
<p>Velocity is the derivative of position, so how can you treat them as independent variables? Doesn't every physics student ask this question when he learns calculus of variations? Does anybody ever answe... | 505 |
<p>Inspired by <a href="http://physics.stackexchange.com/questions/234/how-should-a-physics-student-study-mathematics">How should a physics student study mathematics?</a> and in the same vein as <a href="http://physics.stackexchange.com/questions/193/best-books-for-mathematical-background">Best books for mathematical b... | 4,615 |
<p>If a rectangular pan has a constant and uniform temperature $T$ first, then put it in a vacuum. Considering the effect of thermal radiation, the temperature distribution of the rectangular blackbody will change. My question is, will the temperature of the corner be higher than the edge?</p> | 4,616 |
<p>As the air molecules are environment for carrying sound waves, could stream of photons be environment for carrying electromagnetic waves? What contradictions cause this assumption in the existing theories?</p> | 4,617 |
<p>All around I read that buoyancy is numerically equal to the weight of fluid <strong>displaced</strong> by a submerged object, the volume of displaced fluid being equal to that of the <strong>submerged portion</strong> <a href="https://en.wikipedia.org/wiki/Archimedes%27_principle" rel="nofollow" title="Wikipedia - A... | 151 |
<p>What are the physics of wind (or any gas flow really) bouncing off surfaces?</p>
<p>If a wind hits a wall directly (in a 90 degree angle) does any of it bounce back? </p>
<p>Are there any similarities with, say, light rays hitting a mirror?</p>
<p>I understand, that the other extreme case is a 0 degree angle in g... | 4,618 |
<p>In a Leyden jar, I have read that a charged object is brought in contact with the conductor in contact with the metal inside the jar, thus giving the inner metal a similar charge. And the metal outside the jar then gets an opposite charge.</p>
<p>My question is simply how does the metal outside the jar get the oppo... | 4,619 |
<p>Earlier today, I saw <a href="http://www.orlandosentinel.com/business/nationworld/sns-bc-eu--breakinglightspeed,0,5266439.story">this link</a> on Facebook about neutrinos going faster than the speed of light, and of course, re-posted. Since then, a couple of my friends have gotten into a discussion about what this m... | 83 |
<p>A teacher of mine told me once that there were no ninth gluon because such a one should be white and interact infinitely far, and no one has been observed. Is there also a theoretical reason?</p> | 4,620 |
<p>The derivation for Heat Equation I am reading starts by stating </p>
<p>Net change of heat inside $[x,x+\Delta x]$ = Net flux of heat across boundaries + Total heat generated inside $[x,x+\Delta x]$ and writes the conservation equation</p>
<p>$$\textit{Total Heat Inside} [x,x+\Delta x]=
cpA \int _{ x}^{x+\Delta ... | 4,621 |
<p>I am still struggling with C being a constant and what that implies.
So can an experiment be done to find the resting state for the universe?
Take a device with an observer and a light source and two mirrors, one 10 meters in front and the other 10 meters behind the light source. Now move this through space at some... | 4,622 |
<p>I know it is hard , but can we transfer the charge on a capacitor plate elsewhere? </p> | 4,623 |
<p>The usual "proof" entropy is a state property is like that:</p>
<p>"Consider a system which undergoes a reversible process from state 1 to state 2 along path A, and let cycle be completed along path B, which is also reversible. Since the cycle is reversible we can write: </p>
<p>$$\int_1^2 \delta Q / T + \int_2^1 ... | 4,624 |
<p>I was doing some simple harmonic motion problems and I came across this <a href="http://i.imgur.com/W2zi40o.jpg" rel="nofollow">picture</a> describing the position, velocity and acceleration of a linear oscillator. At the moment in time when v is 0 the linear oscillator should not be moving, only changing directio... | 152 |
<p>Isn't speed a relative thing in space? If so, why would the speed of a propellant matter? Why can't a space ship accelerate infinitely?</p> | 4,625 |
<p>I'm current developing cargo loader software, but i have a little challenge with calculating load for each axle when a cargo is placed on container. I know that all axles will be affected (the nearest ones are the most affected ones of course), and I want to find approximately the value of each load. Here's example ... | 4,626 |
<p>The question I am working on is, "Two blocks are free to slide along the friction-less wooden track shown below. The block of mass $m_1 = 4.98~kg$ is released from the position shown, at height $h = 5.00~m$ above the flat part of the track. Protruding from its front end is the north pole of a strong magnet, which re... | 44 |
<p>Ok, so I remember reading that every conservation law has a corresponding symmetry (i.e. conservation of momentum is translational symmetry, conservation of angular momentum is rotational symmetry).</p>
<p>Now conservation of energy is temporal symmetry (you can rewind the tape and it looks exactly the same, but in... | 4,627 |
<p>What is the orbital motion where both foci are located at one point? I know that an ellipse orbit is motion with two distinct foci.</p> | 4,628 |
<p>I have this problem:</p>
<p>A 4.0 kg block is given an initial speed of 8.0 m/s at the bottom of a 20° incline. The
frictional force that retards its motion is 15.0 N. (a) If the block is directed up the
incline, how far does it move before stopping? (b)Will it slide back down the incline? </p>
<p>... | 4,629 |
<p>I have been told that trasverse wave propogates by the oscillation of medium particles in direction perpendicular to propogation.</p>
<p>Consider a wave on a taught string (x-y plane).
What is the mechanism of movement of the same sinosudial function along the string?</p>
<p>Suppose we start moving the particle o... | 4,630 |
<p>When we send an electromagnetic short wave to the sky, it reflects due to the ionosphere effects. But if we send it horizontally, is it correct that it moves around the surface of the earth, and if it has enough energy, it can return to its first position?</p>
<p>If yes, then how could that happen?</p> | 4,631 |
<p>Thermodynamic buoyancy. I have an air intake for combustion air entering into a basement furnace room. During cold weather, the air enters unchecked (no damper on pipe is allowed). I have this 5 foot vertical pipe, suspended downwards within a 2 foot high box, terminating 12" from the bottom. The cold air spills... | 4,632 |
<p>How is spacetime depicted in quantum field theory?
Is space and time completely separate, and time is just nature of law as in Newtonian mechanics?</p> | 4,633 |
<p>This is an ultra-soft question about relatively recent history. While reading some of Mandelstam's papers, I noticed that he cites David John Candlin consistenly whenever he does anything with Grassman path-integral. Everyone else cites Berezin.</p>
<p>So I read Candlin's 1956 paper, and I was stunned to find a com... | 4,634 |
<p>I live in Ireland where serving food on hot plates is considered “good cooking practice” to ensure the food remains warm – I come from France where I have rarely seen it done.</p>
<p>I am wondering if this practice really is useful. I assume it depends on the difference of temperature between the food and the plat... | 4,635 |
<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/29805/richtmyer-meshkov-instability-in-mhd">Richtmyer Meshkov instability in MHD</a> </p>
</blockquote>
<p>The Richtmyer Meshkov instability in Hydrodynamics:-
1) When shock wave interacts with the conta... | 462 |
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