question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Let's take an CIE XYZ color space as an example. There are many colors that are outside our gamut - how do we see such a color?</p> | g13320 | [
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<p>I am confused by different papers I have seen on the internet. Some say there are three valence quarks and an infinite of sea quarks in a proton. <a href="http://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/" rel="nofollow">Others say</a> there are 3 valence quarks but a larg... | g13321 | [
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<p>I know that matter (mass) curves spacetime, but do other forms of energy do the same? I.e. is matter the only form of energy that curves spacetime?</p> | g143 | [
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<p>In classical field theories, it is with no difficulty to imagine a system to have a continuum of ground states, but how can this be in the quantum case?<br>
Suppose a continuous symmetry with charge $Q$ is spontaneously broken, that would means $Q|0\rangle\ne0$, and hence the symmetry transformation transforms conti... | g13322 | [
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<p>When a bat hits a ball, consider two cases:</p>
<p>1) The batsman goes for a defense, and stonewalls it, to reduce its speed.</p>
<p>2) the batsman goes for a shot, e.g. a home-run, etc.
in which case will the bat have the highest chance of breaking due to the impact?
And am I right in assuming that the force on t... | g13323 | [
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<p>So, I have the problem of determining the spectrum of H and L, in terms of creation and annihilation operators of angular momentum... The problem goes along with what is happening on <a href="http://www.its.caltech.edu/~hmabuchi/Ph125b/Notes2-12v2.pdf" rel="nofollow">this page</a>. However, my professor is asking ... | g13324 | [
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<p>Perhaps this is obvious to the not so tired one, but is there any reason why the five spin 2 polarization tensors $\epsilon_{\mu\nu}^{a}, a=1,\dots,5$ should be symmetric in $\mu\nu$?</p>
<p>While I'm at it, perhaps I should also ask where the tracelessness condition:
$$g^{\mu\nu}\epsilon_{\mu\nu}^{a}=0.$$</p>
<p... | g13325 | [
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<p>If the kinetic energy at maximum height is 2/5 the kinetic energy at half the maximum height, find the angle of projection.</p>
<p>In other words: K.E. at H(max) = 0.4*K.E. at 0.5*H(max)</p>
<p>I got 60 degrees, however, my teacher told me that the answer is 30 degrees. Please solve it for me so I can see where I ... | g13326 | [
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<p><img src="http://i.stack.imgur.com/mRDkD.png" alt="Original illustration by me. Use as you please"></p>
<p>In short: the question is, does the length of the path affect the outcome of detecting a photon?</p>
<p>Consider the single photon beam splitter experiment. Does the probability of detecting the photon change... | g13327 | [
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<p>I am reading this book:<a href="http://www.flipkart.com/solid-state-electronic-d3evices-6ed-6th/p/itmdytczshhgnypr?pid=9788120330207&cmpid=content_book_8965229628_gmc_pla&tgi=sem,1,G,11214002,g,search,,19319548220,1o1,,,c,,,,,,,&gclid=CLPkvYSDpL0CFUUF4god8jwAjw" rel="nofollow">Solid State Electronic Devi... | g13328 | [
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<p>I know the electromagnetic force is mediated by a photon and the weak nuclear force is mediated by two massive bosons. Are there any other insights into why the masses are so different?</p> | g13329 | [
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<p>An electric train accelerates uniformly from rest to a speed of 20m/s which it maintains until the brakes are applied. It is then brought to rest by a uniform retardation equal in magnitude to twice its former acceleration. The total distance covered is 7.8 km and time taken is is 7 minutes. </p>
<p>Calculate </p>
... | g13330 | [
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<p>Our coffee machine catches the last couple of droplets, after your cup is removed on a shape to reduce plash of the coffee droplets. </p>
<p>These shapes are placed inside the spill reservoir.<br>
The shape used by our coffee machine is shape nr 2 with the droplet falling at position 1, this works well but not per... | g13331 | [
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<p>From the first man to the present day men, all of them have made some sound. Sound is an energy, it can neither be created nor can it be destroyed. Therefore, every word spoken by each human that came into this world made some sound. Their voices might have converted into another form of energy. But, we have not los... | g13332 | [
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<p>In The Dark Knight, at the end of the movie Batman throws the Joker off of a building and then shoots his grapple hook gun to catch him. Is 68m/s a reasonable speed for a grapple gun to shoot?</p> | g13333 | [
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<p>I saw this video of a lecture by Feynman where he said that electrons behave like particles when there is a photon source to detect which slit they pass through. Does this imply that electrons mostly behave like particles, since the real world is full of such possible interactions that would destroy interference?</p... | g13334 | [
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<p>I'm confused as to how the above phenomena can take place since arent they breaking the law of conservation of energy (even, if temporarily)?</p> | g13335 | [
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<p>The Heterotic string state is a tensoring of the bosonic string left-moving state and the Type II string right-moving state. Therefore, I expect the spectrum to be:
$$\begin{array}{*{20}{c}}
\hline
& {{\rm{Sector}}}&{{\rm{Spectrum}}}&{{\rm{Massless fields}}}& \\
\hline
& {{\rm{Bosonic}} - {\rm{R}... | g13336 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/7446/travelling-faster-than-the-speed-of-light">Travelling faster than the speed of light</a><br>
<a href="http://physics.stackexchange.com/questions/30505/someting-almost-faster-than-light-traveling-on-so... | g109 | [
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<p>Suppose $D\subset \Bbb R^3$ contains a fluid and that $f : D\times \mathbb{R}\to \mathbb{R}$ is a time dependent function defined on the fluid region. In that case, the material derivative is defined by</p>
<p>$$\dfrac{D}{Dt}f(a, t) = \dfrac{\partial f}{\partial t}(a, t) + (\mathbf{u}\cdot \nabla)f(a, t)$$</p>
<p... | g13337 | [
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<p>I was wondering, from where does the opposite force and thus energy comes from when we apply force.</p>
<p>For example, lets say there are two persons (P1 and P2) on the universe, and no force is applied to them. P1 applies a force to P2. P2 will start to move. P1 lost some energy to do that.
Now, according to the ... | g13338 | [
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<p>In the Gravity movie discussions we learn that objects accellerated towards an object in the same orbit miss it and move to a higher orbit. Objects accellerated away from an object in the same orbit move to a lower orbit.
What shape would an explosion be in orbit?</p>
<p>Edit. Compared to an explosion in space that... | g13339 | [
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<p>I was surfing through an Olympiad paper and I was caught with this question.</p>
<blockquote>
<p>A block of mass 1 kg is stationary with respect to a conveyor belt that is accelerating with $1\, \tfrac{m}{s^2}$ upwards at an angle of 30° as shown in figure. Determine force of friction on block and contact force b... | g13340 | [
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<p>I'd like to write a program that uses the exact (down to the second) amount of time from one new moon (or full moon) to the next.</p>
<p>Yet, I am told that this period is irregular.</p>
<p>Yet, it seems to be predicted in a number of places (ie, by the navy). How do they do this?
<a href="http://aa.usno.navy.mil... | g13341 | [
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<p>I'm working on a post against a recent creationism article about blue stragglers. From when I was in undergrad, the general explanation was that they were likely second generation stars within globular clusters. More recent work seems to indicate that it's likely due to binary interactions with a sun-like star sip... | g13342 | [
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<p>I would love to know! I can find lots about the mass-velocity dispersion relation. There's a mass-luminosity relation (but not really tight). I hope you can include references, as I'm spending hours looking for this and not finding answers.
thanks</p> | g13343 | [
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<p>The white/yellow light hits a red case, and the red color is reflected into our eyes since other wavelengths are absorbed.</p>
<p>My question is since both the paint on the case and the white/yellow light have wavelengths, is there any connection to the paint's wavelength and the red wavelength from the light that ... | g13344 | [
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<p>Calculate the minimum Lawson parameter for sustained deuterium-deuterium fusion in a plasma with an energy of 10 keV.</p>
<p>I have been given the above question as part of a homework assignment and help would be much appreciated.</p>
<p>The Lawson parameter is given as $$ n \tau > \frac{12 k T}{<\sigma v&g... | g13345 | [
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<p>The speed of sound depends on the density of the medium in which it is travelling and increases when the density increases. For example, in solids sound travels faster than in liquid and even faster than in gas, and the density is highest in solids, lower in liquids and lowest in gas.</p>
<p>So iron has a density o... | g13346 | [
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<p>I would like to ask the following:</p>
<p>If an observer travels up or down in an elevator on earth, does he experience a horizontal force due to earth's rotation?</p> | g13347 | [
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<p>The Kane mele model is a famous quantum spin hall model on honeycomb lattice (C.L. Kane and E.J. Mele, Phys. Rev. Lett. 95, 226801 (2005)). The Hamiltonian is </p>
<p>$$H = - t\sum\limits_{\left\langle {i,j} \right\rangle \alpha } {c_{i\alpha }^\dagger {c_{j\alpha }}} + i{\lambda _{SO}}\sum\limits_{\left\langle {... | g13348 | [
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<p>I often read that the Lorentz symmetry is manifest in the path integral formulation but is not in the canonical quantization - what does this really mean?</p> | g13349 | [
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<p>Since space and time are the same is it that whatever happens at different positions in space should take place at different time? If what I think is correct consider an electric dipole, the charges are at different positions in space then, can there be electrostatic attraction between the charges even if they are i... | g13350 | [
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<p>Maldacena and Susskind recently proposed a interesting and very suggestive duality between entanglement and topological identification: <a href="http://arxiv.org/abs/1306.0533" rel="nofollow">http://arxiv.org/abs/1306.0533</a></p>
<p>But are such ideas applicable to horizons in general? Can I entangle a black hole ... | g13351 | [
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0.0... |
<p>Einstein 1905 gives the following axiomatization of special relativity (Perrett and Jeffery's translation):</p>
<ol>
<li><p>The laws by which the states of physical systems undergo change
are not affected, whether these changes of state be referred to the one or the other of two systems of coordinates in uniform t... | g13352 | [
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<p>I am not an expert of physics, instead I am more good at chemistry.</p>
<p>I just wanted to ask that how do I prevent shattering of glasses on sudden large temperature changes?</p>
<p>Sometimes, when I have to cool hot test tubes rapidly, the test tubes break down when I place them in water for cooling.</p>
<p>Is... | g13353 | [
0.06458661705255508,
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0.003476239973679185,
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<p>The wikipedia article <a href="http://en.wikipedia.org/wiki/Gauge_bosons" rel="nofollow">http://en.wikipedia.org/wiki/Gauge_bosons</a> describes how in QM exchanges of gauge bosons carry force, and describes how the graviton may also be a gauge boson.</p>
<p>If the observable universe is made of around 10^80 hydrog... | g13354 | [
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<p>The plural form of physical units are always confusing me. I asked some senior students, some of them said we need to use plural form of units but some said units are always singular. </p>
<p>For example, 1 meter is 1 meter. But it is 3 times, should it be 3 meters? I know that if we use the abbreviation form, no p... | g13355 | [
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<p>I am a physics novice.</p>
<p>Google tells me that electron microscopes work much like their optical counterparts -- but the analogy falls apart for me when I think about what I'm "viewing." Obviously, you can <em>see</em> light through the lenses, but what is the "image" analog for electron microscopes?</p>
<p>I... | g13356 | [
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<p>This question has arisen from a wish to understand an end-of-universe scenario: heat death.</p>
<h3>Are time and mass intrinsically linked?</h3>
<p>If so, does time "run slower" (whatever that may mean) in a universe with less mass? And ultimately, in a universe without any mass, just space and energy (photons), t... | g13357 | [
0.06888048350811005,
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<p>Is it possible for information (like 1 and 0s) to be transmitted faster than light? </p>
<p>For instance, take a rigid pole of several AU in length. Now say you have a person on each end, and one of them starts pulling and pushing on his/her end. </p>
<p>The person on the opposite end should receive the pushes and... | g4 | [
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<p>Some weeks ago, there was lots of talk about this CDF paper:</p>
<p><a href="http://arxiv.org/pdf/1101.0034v1">Evidence for a Mass Dependent Forward-Backward Asymmetry in Top Quark Pair Production</a></p>
<p>where they measured a much higher asymmetry than the one predicted in the SM. In trying to understand the p... | g13358 | [
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<p>As I understand it (and admittedly it's a weak grasp), a computer processes information irreversibly (AND gates, for example), and therefore has some minimum entropy increase associated with its computations. The true entropy increase is much greater, and comes from the conversion of electrical energy to heat.</p>
... | g198 | [
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<p>Hey guys,
I have a final tomorrow and I am going over some assignments. One of the questions from the assignment was:</p>
<blockquote>
<p>A photon having 37 keV scatters from a
free electron at rest. What is the
maximum energy that the electron can
obtain?</p>
</blockquote>
<p>Now, I got the right answer ... | g13359 | [
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0.01598978415131569,
0.03260151669383049,
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0.06775341928005219,
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-0.004766355734318495,
0.00672227144241333,
0.054044801741838455,
0.01665925793349743,
-0.01... |
<p>One statement I've heard many times is that QFT is "defined" by the lattice, or that the "only" definition of QFT is on the lattice (when such definition exists, e.g in pure Yang-Mills theory). I've heard that from many people I respect, but I have my doubts. Specifically - the lattice is an algorithmic definition o... | g13360 | [
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0.011872111819684505,
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<p>If a superconducting magnet and appropriate power supply had just enough $I\cdot s$ (current $\cdot$ length) so that when it was perpendicular to the earth's magnetic field, the force of the interaction was just enough to excede the force exerted on the object from gravity. <em>And</em> it was rotating so the angula... | g1003 | [
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<p>We know very well that as the velocity of an object increases, its relativistic mass also increases because of an increase in its energy which is directly equivalent to mass. We also know that the higgs field is responsible for giving mass to particles and in turn the objects make up the particles. According to our ... | g13361 | [
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0.0127451485... |
<p>This is a question that should have a simple answer, but which I can find no proper discussion of in the literature or on the internet.</p>
<p>I start from the assumption that I have a noisy numerical signal with a peak in it - for example amplitude as a function of $x$, i.e. $A(x)$ - and I wish to determine its fu... | g13362 | [
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0.014238564297556877,
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... |
<p>The problem is this:</p>
<blockquote>
<p>A particle is represented by the wave function $\psi = e^{-(x-x_{0})^2/2\alpha}\sin kx$. Plot the wave function $\psi$ and the probability distribution $|\psi(x)|^2$.</p>
</blockquote>
<p>This the problem 2.1 in the book <em>Fundamental University Physics Volume III</em> ... | g13363 | [
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0.04279293492436409,
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0.03095942549407482,
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0.04066694900393486,
0.0099109448492527,
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<p>I'm looking for simple problems in theoretical mechanics that are impossible or unreasonably difficult to solve by means of "brute-force" numerical integration of <a href="http://en.wikipedia.org/wiki/Euler-Lagrange_equation">Newton</a> or <a href="http://en.wikipedia.org/wiki/Euler-Lagrange_equation">Euler-lagrange... | g13364 | [
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<p>Suppose you had an isolated cloud of gas at a low temperature in a vacuum with no external sources of radiation (e.g. no CMB). The gas would clearly cool via the emission of low-energy photons. But where do these photons come from? The thermal energy of the gas is simply manifest as elastic collisions between atoms ... | g13365 | [
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0.0799039751291275,
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-0.0192... |
<p>String field theory (in which string theory undergoes "second quantization") seems to reside in the backwaters of discussions of string theory. What does second quantization mean in the context of a theory that doesn't have Feynman diagrams with point-like vertices? What would a creation or annihilation operator d... | g13366 | [
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... |
<p>Why is it that thermal radiation of a black body usually described by a spectral distribution function rather than an intensity vs frequency curve? </p>
<p>I have a vague explanation for this: Any measured intensity of radiation will contain a spectrum of frequencies which are impossible to separate (even with a ve... | g566 | [
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0.0... |
<p>I am always confused about which temperature to evaluate fluid properties at. Let's say I have a helical pipe and I know the inlet temperature, outlet temperature, and surface temperature and the inlet Reynold's number. I must determine the length of the pipe needed to satisfy the outlet temperature which means I mu... | g13367 | [
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0.01915404386818409,
0.02677425742149353,
0.06... |
<p>4 men weighing 380kg, carrying a 380kg piano up 5 meters will generate 31 watt if the load takes 20 minutes. Now this is very hard to do and saps the strength out of any human being.</p>
<p>However, that barely powers a light bulb...Would I need more than all my strength to power a light bulb??</p>
<p>Thank you.</... | g13368 | [
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0.010902144014835358,
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... |
<p>The analytic solutions of a quantum harmonic oscillator are given by <a href="http://www.google.com/search?as_q=states&as_epq=Hermite+Gauss" rel="nofollow">Hermite-Gauss states</a>, which differ in the order $n$ of the Hermite polynomials. If two such states are plotted, there will be a relative phase shift. How... | g13369 | [
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0.04730261117219925,
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0.016539976000785828,
0.0234... |
<p>I want to apply a <strong>pure</strong> torque to an object, say a square box on the ground. And I also require that the torque is generated on the corner of the square, not the center of mass. Is there any way for me to do that?</p>
<p>I know there is torque motors. But imagine this, if I attach the torque motor t... | g13370 | [
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0.03958294913172722,
-0... |
<p>Why symmetry work in circuits? In my book there is no mention explanation as such for symmetry arguments and circuits. But there are circuits that are very difficult to solve without symmetry. Also I have heard that they save a lot of time. Can anyone please tell me why symmetry works in circuits? And what are some ... | g13371 | [
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-0.05949332192540169,
0.03135... |
<p>I want to find out the linear velocity of a point in 3D space, (Euclidean), given:</p>
<ul>
<li>Its position </li>
<li>Its angular velocity</li>
<li>The point it's rotating around (fulcrum)</li>
</ul>
<p>(This is a problem I need to solve for 3D graphics programming with a physics engine).</p>
<p>The position of ... | g13372 | [
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0.0062124161049723625,
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0.029658349230885506,
0.013969069346785545,
-0... |
<p>Let $\mathscr{I}_3$ and $\mathscr{I}$ are the moments of inertia for rotations about symmetry axis 3 and about an axis perpendicular to it , and I is the angular momentum operator with components $I_1, I_2$ and $I_3$ along the body fixed axis(1,2,3), ,then
,</p>
<blockquote>
<p><strong>How the Hamiltonian can b... | g13373 | [
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0.034743182361125946,
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0.0201713964343071,
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-0.0... |
<p>Simple question. But I was wondering, does my mac power cord create a magnetic field when its all coiled?</p> | g13374 | [
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0.007326231338083744,
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0.... |
<p><strong>The question:</strong> </p>
<p>At temperatures <strong>above ~5000K are not stable any solid or liquid</strong> materials or even more complex molecules (such as fullerenes and Polycyclic aromatic hydrocarbons) <strong>which emit/absorb wide-spectral black-body radiation effectively</strong>. </p>
<p>Simpl... | g13375 | [
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0.006422427482903004,
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0.045496657490730286,
0.06425900757312775,
0.01... |
<p>What prevented all of the hydrogen at the universe's start from coalescing into one gigantic star?</p> | g13376 | [
0.0035544484853744507,
0.026346862316131592,
0.00470690568909049,
0.003961971960961819,
-0.01749815233051777,
0.046657152473926544,
0.003440267639234662,
0.05803540349006653,
-0.05054732784628868,
-0.07114102691411972,
-0.02463447116315365,
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0.05271464213728905,
0.022... |
<blockquote>
<p><em>A old massless rope of 12 meters attached to a ceiling can sustain a maximum tension force of 1200N before breaking. An 85 kg person climbs up the rope. What is the minimum possible time in which he can climb to the top without breaking the rope?</em></p>
</blockquote>
<p>My issue is figuring ou... | g13377 | [
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-... |
<p><img src="http://i.stack.imgur.com/JMjzp.png" alt="enter image description here"></p>
<p>Basically energy of conservation says it doesn't matter what path I take, energy will be the same from before as it is after.</p>
<p>So I took the block at the top's energy equal to the energy when it lands on the ground (when... | g13378 | [
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<p>I know very little about electromagnetic waves and light in general so you are going to have to bear with me. I am attempting to calculate the force on a sphere in a plane wave of light where the light has intensity I. My calculations and research have concluded that, regardless of whether or not the sphere absorbs ... | g13379 | [
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<p>Let's say I have an electromagnetics problem in a spatially varying medium. After I impose Maxwell's equations, the Lorenz gauge choice, boundary conditions, and the Sommerfeld radiation condition, I still have more unknowns than equations and the solution for (say) the magnetic vector potential is not uniquely det... | g13380 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/26083/why-are-our-planets-in-the-solar-system-all-on-the-same-disc-plane-layer">Why are our planets in the solar system all on the same disc/plane/layer?</a> </p>
</blockquote>
<p>I've noticed this in ma... | g231 | [
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0.006163026671856642,
0.07229819893836975,
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-0.003545671235769987,
0.009228065609931946,
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-0.024296699091792107,
0.035569045692682266,
0.019618025049567223,
0.041759882122278214,
0... |
<p>Wikipedia article about Electromagnetic Radiation says "As an electromagnetic wave, it has both electric and magnetic field components". And <a href="http://physics.stackexchange.com/questions/41680/why-is-light-called-an-electromagnetic-wave-if-its-neither-electric-nor-magne">this discussion</a> also confirms Light... | g13381 | [
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<p>A follow-up to my earlier question <a href="http://physics.stackexchange.com/q/31924/5265">How would one navigate interstellar space?</a> that just occurred to me; albeit on a different tack.</p>
<p>Sol is probably in a state of continuous flux. The change of state is probably over large timescales as compared to t... | g13382 | [
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<p>In page 71 Weinberg's QFT, </p>
<p>$$A\Psi^{\theta }_{a,b}
~=~(a\cos{(\theta )}-b\sin{(\theta )})\Psi^{\theta }_{a,b}.$$ </p>
<p>He says that massless particles represented by $\Psi ^{\theta }_{a,b}$ are not observed to have the continuous degree of freedom $\theta$. I do not understand why. </p>
<p>These $\Psi ... | g13383 | [
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<p>I'm wondering what are the validity limits of Multi-Species Navier-Stokes equations. I'm aware of the limit for rarefied gases. But is there any new limit that arises in the context of real gases?
I hope that an answer could be found by making use of the kinetic theory.</p> | g13384 | [
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0.0032962372060865164,
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<p>In classical continuum mechanics, the stress <a href="http://en.wikipedia.org/wiki/Tensor" rel="nofollow">tensor</a> is said to be of type/valence (1,1) and I do not see why.</p>
<p>If I am correct, its maps a vector $n$ defined in $\mathbb{R}^3$ (which is the normal to a given infinitesimal surface) to another vec... | g13385 | [
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<p>Googling around for ways to measure the viscosities of shear thinning liquids, it seems to me that most of the time viscometers are used at different settings to measure different apparent viscosities.
Is this the only strategy out there, did I miss something?</p> | g13386 | [
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<p>For example an electron radiates when accelerated. So does a positron. But is the radiation emitted by accelerated positronium the sum of the radiation emitted by each separately? If not, why not? If so, does this provide a way of testing whether a given neutral particle is composite? For example, does a neutron bre... | g13387 | [
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0.00234008650... |
<p>The <a href="http://en.wikipedia.org/wiki/Higgs_mechanism" rel="nofollow">wikipedia article on the Higgs mechanism</a> states that there is overwhelming evidence for the electroweak higgs mechanism, but doesn't then back this up. What evidence is there?</p> | g13388 | [
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<p>I am trying to fit a polynomial function by least square method and I want to know the uncertainty on my fitting parameters. In which book can I find a clear answer?</p> | g13389 | [
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0.03931839391589165,
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... |
<p>Suppose I want to compute $S^{1}_z -S^{2}_z$ on a singlet state $|0,0>$. (where $S^{i}_z$ are two particles' spin operators). $$|0,0> = \frac{1}{\sqrt{2}} (|\frac{1}{2},-\frac{1}{2}> - |-\frac{1}{2},\frac{1}{2}>).$$ I don't get the correct answer by just computing and using $$S^{1}_z|m_{s1}, m_{s2}> =... | g13390 | [
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0.0591510534286499,
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0.0004319... |
<p>I have a problem in finding the direction of the force when a conducting wire is placed in a magnetic field. If I use <a href="http://image.wistatutor.com/content/feed/u851/rr_2.GIF" rel="nofollow">Fleming's Right Hand rule</a> I get a circular magnetic field, so what will be the direction of force acting on th... | g13391 | [
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<p>I'm doing an assignment and I've been given a list of $4 \times 4$ matrices and asked:</p>
<blockquote>
<p><em>Which of the following are <a href="http://en.wikipedia.org/wiki/Lorentz_group" rel="nofollow">Lorentz transformation matrices</a>? Which are proper
and orthochronous?</em></p>
</blockquote>
<p>But, a... | g13392 | [
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<p>As a followup question to this question: <a href="http://physics.stackexchange.com/q/133012/55779">The relation between energy quanta of an Einstein solid and the equipartition value of heat capacity</a> and this answer <a href="http://physics.stackexchange.com/a/133053/55779">http://physics.stackexchange.com/a/1330... | g13393 | [
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... |
<p>If a solid sphere is moving vertically down with a velocity $v$ and spinning with an angular velocity $\omega$, what is the angular momentum of the sphere about an axis through the sphere which is at a distance $ \frac{R}{2}$ vertically below the center of mass of the sphere ?</p> | g13394 | [
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<p>Do physicists ever expect to be able to derive the fundamental constants of nature from theory? For example, if string theory or some other theory unites the four forces, would the theory be considered complete if it relies on these measured constants, or would a true theory of everything (TOE) require that these c... | g13395 | [
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<p>I was just reading a Nature news article (<a href="http://www.nature.com/news/entangled-photons-make-a-picture-from-a-paradox-1.15781#/b1" rel="nofollow">Entangled photons make a picture from a paradox</a>, 27 August 2014) about a way to form an image of an object out of photons that have not interacted with the obj... | g13396 | [
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<p>Although I find it mathematically dubious, we said that $\Delta \frac{1}{r} = -4\pi \delta(r)$. Now, I was wondering is there a similar relation to the delta function if we look at $\Delta \frac{1}{r^n} =?$. </p> | g13397 | [
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<p>I've been thinking to this for the last two hours and haven't been able to come with a solution. </p>
<p><strong>Problem.</strong> A mole of gas initially at pressure $P_A = 2 \text { atm}$ and occupying a volume $V_A=20\,\text {L}$, passes through an irreversible transformation in which it absorbs $Q=1200J$ as hea... | g13398 | [
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... |
<p>Is there a convention for naming the vectors?</p>
<p>Suppose there is a box on a table. I'm going to draw the forces acting on the box. So I focus on the box and ignore forces acting on the table, the normal vector on the box is named after the box or the table? My doubt is, subscript $B$ to mean "normal vector act... | g13399 | [
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<p>We know the non-dimensionalized distance of the viscous sub-layer is 5 wall units for a turbulent boundary layer. It is common to see this in Fluid Mechanics books but seems somewhat arbitrary.</p>
<p>I want to know if this true for all conditions or does it depend on the Reynolds number (high viscosity, high speed... | g13400 | [
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<p>A little bit of background information: I'm planning to write a little booklet or web page about CPU/computer architecture, basically for my own education, because we didn't cover it in depth in college. I feel like I should be learning a lot more about the fundamentals about how computers work, if I want to be a be... | g13401 | [
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<p>My question is a 2 part question.</p>
<p>First if a vessel in space is going very fast and suddently stops (maybe it is not possible but that is not the point) will things/humans inside the vessel keep going forward or stop with the vessel?</p>
<p>Is it the same if the cabin is oxygened or not?</p>
<p>I know the ... | g13402 | [
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<p>I'm trying to understand why you can't write down a first order equation of motion for a scalar field in special relativity.</p>
<p>Suppose $\phi(x)$ a scalar field, $v^{\mu}$ a 4-vector. According to my notes a quantity of form $v^{\mu}\partial_{\mu}\phi(x)$ will not be Lorentz invariant. </p>
<p>But explicitly d... | g13403 | [
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<p>Is there a notion of measurement, which doesn't correspond to a yes/no question or with the idea of the comparison of two real world objects, which produces a real number? </p>
<p>And does at least one of the object which are compared to produce the measurement result have to be modeled within the theory? </p>
<p>... | g13404 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/6400/are-tidal-power-plants-slowing-down-earths-rotation">Are tidal power plants slowing down Earth's rotation?</a> </p>
</blockquote>
<p>I've heard that there are turbines converting energy from tid... | g349 | [
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... |
<p>This is a question about deriving effective mass theory for graphene. For the two sub-lattice atoms, the wave equation can be written as the massless Dirac equation: </p>
<p>$ \displaystyle -i\hbar v_F \begin{pmatrix} 0 & \partial_x -i\partial_y \\\partial_x +i\partial_y & 0 \end{pmatrix} \left(\begin{array... | g13405 | [
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<p>The laws of physics are invariant under <a href="http://en.wikipedia.org/wiki/CPT_symmetry" rel="nofollow">CPT</a> transformations <a href="http://en.wikipedia.org/wiki/T-symmetry" rel="nofollow">reversing time</a>, inverting space and flipping charges. Almost so. The <a href="http://en.wikipedia.org/wiki/Wave_funct... | g13406 | [
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<p>Why the wave function collapse corresponds to a non-unitary quantum operation?</p> | g13407 | [
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<p>Looking at the radius and mass of stars on Wikipedia, I see that the Sun is the densest of all, often many times denser than other stars. Is that because only non-dense starts are easily seen from a distance? Are there any stars of comparable luminosity to the sun that can be seen with the naked eye, and do they hav... | g13408 | [
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<p>Conservation of probability: Suppose a wavefunction has ${\partial \mathbb P \over \partial t} = -t f(x,t)$ and ${\partial j \over \partial x} = i f(x,t)$. How does it follow that ${\partial \mathbb P \over \partial t} = {-\partial j \over \partial x}$? Thanks.</p> | g13409 | [
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<p>Can someone give me questions on physics because I have my Examination tomorrow
Class 9th (CBSE)
topic : - Fluids(Density,buoyant Force , Archemedis Principal) , Work Power Energy(Work Basics, potential Energy, Kinetic Energy, Conservation of energy) , Sound(Sound Basics).Thanks in Advance</p> | g13410 | [
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<p>There have been previous questions (e.g. <a href="https://physics.stackexchange.com/questions/1720/ice-skating-how-does-it-really-work">here</a> and <a href="https://physics.stackexchange.com/questions/81561/why-can-we-skate-on-ice">here</a>) on Physics.SE about the mechanism that makes ice skating possible. Reviewi... | g13411 | [
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