question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>I am studying an example problem, concerning the very topic mentioned in the title. In this example problem, a car has a head-on collision with the wall; the initial and final velocity are known, as well as the mass. My question is, why does the car rebound off of the wall? Why doesn't the normal force of the wall r... | g9168 | [
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<p>I was playing around with <a href="http://www.lpta.univ-montp2.fr/users/kneur/Suspect/">SuSpect</a> to generate some SUSY mass spectrums and I'm often encountering situations where I get a negative neutralino mass. </p>
<ol>
<li><p>What is the physical meaning of this negative mass I am getting? </p></li>
<li><p>Do... | g9169 | [
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<p>I'd like to calculate the distance between the Earth and an asteroid at a given date. Is this possible using the data from <a href="http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=433" rel="nofollow">JPL's small-body database</a>? Is there a better way?</p> | g9170 | [
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<p>This might be an incredibly naive question, but I'm wondering if there are a set of rules for "translating" between Standard Model and SUSY. For instance, if I want want to go from a Standard Model feynman diagram to a SUSY diagram, can one write down a set of rule including things like:</p>
<p>"replace quarks with... | g9171 | [
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<p>I was attempting to do some calculations of apparent magnitude to help solidify my understanding of the topic, but have been running into some confusion.</p>
<p>According to <a href="http://en.wikipedia.org/wiki/Apparent_magnitude#Calculations" rel="nofollow">Wikipedia</a>, the apparent magnitude can be given as:</... | g9172 | [
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<p>When we first learn elementary geometrical optics, the first thing taught to us is the two broad divisions of the type of reflection.-Regular and Irregular or Diffused.<br>
The difference in cause for both of these is that in case of regular reflection an incoming ray is perfectly reflected in a specific direction b... | g9173 | [
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<p>In his QFT book, Weinberg claims what follows (Vol I, pag. 144-145): given a (free) representation of the Poincaré group with generators $\bf P$ (spatial translations), $H_0$ (time translations), $\bf J$ (rotations), and ${\bf K}_0$ (boosts), one obtains another (interacting) reprentation by replacing $H_0$ and ${\b... | g9174 | [
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<p>I study physics and am attending a course on quantum field theory. It is hard for me to draw connections from there to the old conventional theories.</p>
<p>In quantum field theory spin originates from the Dirac equation in the case of fermions. </p>
<p>I don't remember where it comes from in quantum mechanics. I ... | g824 | [
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<p>Non-unital completely positive (<a href="http://en.wikipedia.org/wiki/Choi%27s_theorem_on_completely_positive_maps" rel="nofollow">CP</a>) maps take a maximally mixed quantum state (aka a normalized identity matrix aka an infinite temperature state) and map it to something else. This necessarily decreases its von N... | g9175 | [
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<p>It is experimentally known that the equation of motion for a charge $e$ moving in a static electric field $\mathbf{E}$ is given by:</p>
<p>$$\frac{\mathrm{d}}{\mathrm{d}t} (\gamma m\mathbf{v}) = e\mathbf{E}$$</p>
<p>Is it possible to show this using just Newton's laws of motion for the proper frame of $e$, symmetr... | g9176 | [
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<p><strong>1.a</strong> In paragraph at <a href="http://en.wikipedia.org/wiki/Entropy#Relating_entropy_to_energy_usefulness">Wikipedia/Entropy</a> it is stated:</p>
<blockquote>
<p>This is because energy supplied at a <strong>high temperature (i.e. with low entropy)</strong>
tends to be more useful than the same a... | g9177 | [
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<p>I read a few times that a knot can reduce the strenght of a rope, but I can't understand why this happens. Can someone explain me what happens to a rope tied with a generic knot and stretched? Is there a way to calculate the reduction of resistance from the form of the knot?</p> | g9178 | [
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<p>First of all, does the expansion of spacetime solely cause the expansion of universe?</p>
<p>Secondly, if spacetime is the sole cause, do objects(matter with mass) themselves expand?</p>
<p>Thirdly, by spacetime expansion, does time also expand? (at least in general relativity)</p>
<p>Thanks.</p> | g56 | [
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<p>A hydrogen atom is characterized by the wavefunction</p>
<p>$$\mid \psi \rangle =\sqrt{\frac{2}{7}}\mid 4\,2\,1\rangle +\sqrt{\frac{1}{7}}\mid 2 \,1\,\bar{1}\rangle+\sqrt{\frac{4}{7}}\mid 3\,2\,0\rangle$$</p>
<p>I want to know the possible outcomes and the probability for obtaining each outcome from measuring $E$,... | g9179 | [
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<p>If the earth left the solar system for some reason. Assuming its moving at the same velocity it's currently exhibiting. How long would it take for the atmosphere to freeze. Would we get methane clouds like Titan. Would there be an atmosphere or would it all be frozen on the ground? </p> | g918 | [
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<p>If we have a sphere which has $σ$ surface charge density and rotate it in axis z will this create current ? Is it possible without any potential difference ? </p> | g9180 | [
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<p>I've been digging into emission spectra of different elements and found that such things as the Rydberg equation, Bohr's model, and quantum mechanics can only fully describe the single electron in the Hydrogen atom. How did we then make the leap to s,p,d,f shells of multi-electron atoms? How accurate is our analysis... | g9181 | [
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<p>At a very basic level I know that gravity isn't generated by mass but rather the <a href="https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor">stress-energy tensor</a> and when I wave my hands a lot it seems like that implies that energy in $E^2 = (pc)^2 + (mc^2)^2$ is the source of gravity.</p>
<p>If the to... | g112 | [
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<p>In quantum electrodynamics, the classical Hamiltonian is obtained from the classical electromagnetic Lagrangian. Then the classical electric and magnetic fields are promoted to operators, as is the classical 4-vector potential $A_{\mu}$. The appropriate commutation relations are expected between the fields and their... | g9182 | [
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<ol>
<li><p>If gravity is the force of attraction between masses, does this force is an intrinsic property of every atoms? </p></li>
<li><p>Is there any possibility of some other particles within atom which is yet to be discovered? </p></li>
<li><p>Or is it simply a result of cosmic waves which created due to big bang?... | g9183 | [
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<p>In <a href="http://www.youtube.com/watch?v=EYPapE-3FRw" rel="nofollow">this video of Feynman discussing the scientific method</a>, starting at around eight minutes and 30 seconds, Feynman describes the proposition that space consists of a cubic lattice of points (as opposed to space being continuous). Feynman says ... | g114 | [
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<p>Are there any theories out there that discuss the idea that space itself could be made out of particles?</p> | g302 | [
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<p>I can't find an answer of why the lowest temperature is -273.15ºC. Is it deduced theoretically or is it experimental?</p>
<p>An explanation is that when any gas volume tends to zero, the temperature will be -273.15ºC (Charles law). But shouldn't this number have some kind of error? And this would only apply to idea... | g9184 | [
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<p>I know that
$A_{[a} B_{b]} = \frac{1}{2!}(A_{a}B_{b} - A_{b}B_{a})$</p>
<p>But how can write $E_{[a} F_{bc]}$ like the above?</p>
<p>Can you provide a reference where this notational matter is discussed?</p> | g9185 | [
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<p>Why do hurricane winds rotate? I know it´s about <a href="http://en.wikipedia.org/wiki/Coriolis_effect" rel="nofollow">Coriolis force</a> but how can I be quantitative? My problem is that I can´t imagine the direction velocity of wind and the angle with earth angular velocity rotation. Also, when can we explain oth... | g9186 | [
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<p>I am looking for an introduction (textbook or paper, or if someone wouldn't mind writing a memo on it) to canonical quantum gravity, specifically the concept of minisuperspaces. I have been reading the paper of Wheeler (in Phys Review) but he doesn't speak about minisuperspaces, maybe they were not used/invented at ... | g9187 | [
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<p>The circuit under consideration has two inductively coupled loops, one with a DC battery, inductor, and resistor in series. The other loop has two inductors, one inductively coupled to the first, the other not, and a resistor, all in series. </p>
<p>I would like to know the current in the top loop (the one without ... | g9188 | [
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<p>Let me create a very artificial experimental set up. Take a bathtub the size of Delaware and suspend it a mile above the ground. Fill it with water (though I'm not sure to what depth - and it might matter). Now pull the plug out.</p>
<p>The effect is that you have a waterfall with an endless supply of water, high a... | g9189 | [
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<p>Will a plant grow faster when you would apply more upward gravitational force?</p>
<p>and/or</p>
<p>Will a plant grow slower when you would apply more downward gravitational force?</p> | g9190 | [
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<p>I'm interested in a QFT model featuring a fermion derivative coupling like $XX^* \chi^*\gamma^\mu∂_\mu \psi$ where X is some other field operator.
Has anybody seen a paper containing something like this?
How would Feynman-Graphs for such an interaction look like?
Are derivatives of fermions ruled out by some conside... | g9191 | [
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<p>Is there field theory which describe a second order phase transition without upper critical dimension ? Mermin-Wagner says something about lower critical dimension but nothing about upper dimension.</p> | g9192 | [
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<p>I'm a beginner in quantum mechanics, and I'm a bit confused about states and the probability to measure certain values. I would like to understand at least the following simplified situation:</p>
<p>Suppose the operator $S_z$ is measuring the spin in the $z$ direction of a free particle. Let $$\{e_s\},\quad s = -L... | g9193 | [
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-0.016454756259918213,
-0.035557493567466736,
0.0014177471166476607,
-0.011779804714024067,
0.08028176426887512,
0.053036801517009735,
0.033808402717113495,
-0.02984549105167389,
-0.030752811580896378,
-0.0013419481692835689,
0.0502779595553875,
... |
<p>Can anyone explain what metric signature is?</p>
<p>I have a basic knowledge regarding tensors, btw.</p>
<p>Also, how is it related to fundamental understanding of general relativity?</p>
<p>Thanks.</p> | g9194 | [
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0.09935527294874191,
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<p>How do <a href="http://en.wikipedia.org/wiki/Stirling_engine" rel="nofollow">Stirling engines</a> work? I understand the heating and cooling of air, but how much faster (or more force, I'm not sure which to use) does the piston move per degree Celsius that the temperatures differ?</p> | g9195 | [
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<p>So for a complex dielectric constant $\epsilon = \epsilon_a + i\epsilon_b$, the wave vector and index of refraction are related to it through $k = \frac{\omega}{c}n$ and $n = \sqrt{\frac{\mu \epsilon}{\mu_0 \epsilon_0}}$. According to Jackson, the real part of the dielectric is related to polarization and anomalous ... | g9196 | [
0.013967575505375862,
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0.02582796849310398,
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0.011729877442121506,
0.03226381167769432,
0.022674... |
<p>What is the physics behind a normal human jump ?</p>
<p><img src="http://www.wired.com/images_blogs/wiredscience/2012/04/drawings_spring_12key_23.jpg" alt="a human jump"></p>
<p>when a normal human wants to jump.</p>
<ol>
<li>First, some energy is stored in their thighs and The elastic tendons Just like a spring.... | g9197 | [
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<p>I always thought that high voltage power lines would attract a lightning strike more than other structures in the same area. Turns out I was wrong. My neighbor's chimney got struck by lightning and it destroyed a lot of stuff (street lamps, wifi APs, small home electronics). We live very close to high voltage power ... | g9198 | [
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0.0... |
<p>This question follows on previous work on connections between (other) areas of physics and thermodynamics as in <a href="http://physics.stackexchange.com/q/115026/">here</a>, <a href="http://physics.stackexchange.com/q/114697/">here</a> and <a href="http://cs.stackexchange.com/q/26049/">even here</a>.</p>
<p><a hre... | g9199 | [
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0.011188192293047905,
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... |
<p>I'm aware of the so-called <a href="http://en.wikipedia.org/wiki/Refractive_index#Group_index" rel="nofollow">group index</a> but why is the phase velocity used in the <a href="http://en.wikipedia.org/wiki/Refractive_index#Definition" rel="nofollow">standard definition</a> of the index of refraction? What advantage ... | g9200 | [
0.007063641212880611,
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0.01... |
<p>Sorry, since the question has been posed, but I insist that others posed not from this position.</p>
<p>Can any listener deduce whether we could measure, by analyzing electromagnetic disturbance, a particle$^1$ traveling faster than light? (or current measuring device, for the sake of assuming for questioning)</p>
... | g9201 | [
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0.006593951489776373,
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0.03173636645078659,
0.0283... |
<p>The limit of microscopes is 200nm, but apparently STED improves this according to this coverage of the Kavil prizes 2014 : </p>
<p><a href="http://www.photonics.com/Article.aspx?AID=56255" rel="nofollow">http://www.photonics.com/Article.aspx?AID=56255</a> </p>
<p>What is the current limit for microscopy ? </p> | g9202 | [
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-0.... |
<p>I have searched the internet and have not found any actual test results.</p> | g9203 | [
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... |
<p>While deriving lagrange's equation, for an infinitesimal displacement $\vec{dr}$, we express it using taylor series in terms of general coordinates as $\frac{\vec{dr}}{dq} \delta q$. Where $\frac{\vec{dr}}{dq}$ means derivative of $\vec{r}$. What does it mean?(this derivative term). What is the function whose deriv... | g9204 | [
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<p>we are given a problem with spring with its own mass $m$. I am confused how to set up the
PE term in the Lagrangian.</p>
<p>Assume the spring has length of $L_{0}$ when it is laying on a table
horizontally. Now when we hold the spring upright and hang it vertically from
a pivot in the ceiling to make a pendulum, it... | g9205 | [
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0.0... |
<p>Are the ions in a fluorescent lamps concentrated near the electrodes , and just the electrons move to the other electrode or the positive mercury ions move too?</p> | g9206 | [
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<p>An electron is orbiting two protons. With the Born-Oppenheimer approximation that the protons do not move, I'd write the Hamiltonian of the electron's movement as:</p>
<p>$$ \mathbf{H} = -\frac{\hbar^2}{2m}\nabla^2 + E_p$$</p>
<p>with</p>
<p>$$E_p = -\frac{e^2}{4\pi \epsilon_0}\left(\frac{1}{r_1}+\frac{1}{r_2}\ri... | g9207 | [
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<p>I want to know if dimensional regularization has any issues if the theory has IR divergences or is scale invariant. </p>
<ul>
<li><p>Does dimensional regularization see "all" kinds of divergences? </p>
<p>I mean - what does it <em>exactly</em> mean when one says that power law divergences and IR divergences disapp... | g9208 | [
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<p>Kinetic energy conservation in collision.</p>
<p>In any type of collision type of collision if we take the system to comprised of both bodies then the net external force is zero. So the work done by external force is also zero. By the relation $W=K_f-K_i$ as $W$ is zero hence kinetic energy is conserved. But this n... | g9209 | [
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<p>I wonder whether $\sigma$ or $\sigma / \sqrt{N}$ is error of a measurement. When I measure, say $0, 1, -1, 1, -1$, I have a $\sigma = 1$. I just measure $0, 1, -1$, I also have $\sigma = 1$.</p>
<p>But in the former case, I had more measurements, so the error should be smaller. So would the error be 1 or rather $1/... | g9210 | [
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0... |
<p>Does <a href="http://en.wikipedia.org/wiki/Chaos_theory">chaos theory</a> occur in quantum mechanics? Or in any non-newtonian physics? Apart from perhaps thermodynamics?</p> | g9211 | [
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<p>Good evening,</p>
<p>I haven't had physics since year 7 and now I need to use elementary things in university. Since I lack a lot of basics I am now trying my best to fill these holes. Currently I am stuck at solving circuits and I hope one of you can help me with the following circuit. I've also attached an image ... | g9212 | [
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... |
<p>Is there any dependence of the impurities ionization energy on temperature in silicon? I mean if there are any interactions between localized electron and phonons which leads to renormalization of electron binding energy.</p> | g9213 | [
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<p>Liquid-gas transition critical point is believed to share the same universality class as the 3D Ising model.</p>
<p>We know that the liquid-gas transition is characterized by a phenomenon called critical opalescence that occurs at the critical point and which in short happens because the system becomes correlated a... | g9214 | [
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<p>I really like to do research in physics and like to calculate to see what happen. However, I really find it hard to write a paper, to explain the results I obtained and to put them in order. One of the reasons is the lack of my vocabulary. </p>
<p>How do I write physics well? I think that writing physics is more de... | g9215 | [
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<p>(for a more muddled version, see physics.stackexchange: <a href="http://physics.stackexchange.com/questions/14020/whats-with-mandelstams-argument-that-only-linear-regge-trajectories-are-stable">http://physics.stackexchange.com/questions/14020/whats-with-mandelstams-argument-that-only-linear-regge-trajectories-are-st... | g9216 | [
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-... |
<p>In his work on information processing in GPTs <a href="http://arxiv.org/abs/quant-ph/0508211">http://arxiv.org/abs/quant-ph/0508211</a> Barrett speculates that the trade-off between allowed states and the allowed dynamics in a GPT is optimal in quantum theory, allowing for information processing capabilities not all... | g9217 | [
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<p>It always fascinate me that time is symmetrical classical physics while in life we all experience flow of time in only one direction. There is no preference direction of time in classical physics. The only exception being in thermodynamics where with the introduction of entropy, there is a prefer direction for the t... | g303 | [
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0... |
<p>Why do spinless fermions behave in the same way as weakly interacting bosons.</p> | g9218 | [
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<p>Would we all parish due to excessive heat? Or would that be only limited to the area near the impact while as the people on rest of the earth would die from other phenomenons such as mega earthquakes, volcanic activities, tsunamis etc. Does it matter where the impact is - if it landed in antarctica we would have mas... | g9219 | [
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<p>I would like to know the ballistic device characteristics and illustrations (if any) to understand how can we overcome the dependence of current on carrier mobility .</p> | g9220 | [
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0.09454281628131866,
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0.033... |
<p>I'm performing an experiment with a 2D <a href="http://en.wikipedia.org/wiki/Double_pendulum" rel="nofollow">double pendulum</a>, and in part of it I want to investigate the normal modes of the double pendulum, where the pendula are not of equal length or of equal mass. My question is - how will I actually know when... | g9221 | [
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0.014711612835526466,
0.04324045404791832,
-0.0057... |
<p>Is light electromagnetic waves or quantum physical particle waves. Or are they the same?</p>
<p>Note: My question is specifically how electromagnetism plays into the quantum physics and the double slit experiment.</p> | g304 | [
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0.031... |
<p>Question: The melting point of copper is 1080 degrees Celsius and its heat of fusion is 200 kJ/kg. If a copper coin at this temperature is completely melted by the absorption of 2000 J of heat, what is the mass of the coin in kg?</p>
<hr>
<p>I am not sure which formula(s) to use. Is the melting point even needed ... | g9222 | [
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<p>How is the Lorenz gauge condition $\partial_\mu \overline{h}^{\mu \nu}=0$ equivalent to the <a href="http://en.wikipedia.org/wiki/Harmonic_coordinate_condition">harmonic gauge condition</a> $\Box x^\mu=0 $?</p> | g9223 | [
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<p>How do the wave properties of an electron change with its motion? What about when it is stationary?</p> | g9224 | [
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<p>A student conducts an experiment to measure the motion of two unknown masses (A and B) along a smooth table. A constant force of 1 N was applied by means of a string connected by a falling weight. </p>
<p>A motion sensor recorded the position (measured from the start line) of each mass at regular time intervals as ... | g9225 | [
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<p>When quantizing Yang-Mills theory, we introduce the ghosts as a way to gauge-fix the path integral and make sure that we "count" only one contribution from each gauge-orbit of the gauge field $A_\mu\,^a$, because physically only the orbits themselves correspond to distinct physical configurations whereas the motion ... | g9226 | [
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<p>I'm searching for references, articles and books, that discussed the geometrization of modern (and contemporary) physics, in a philosofical point of view. Something in the way that Michael Friedman did in "Space-time foundations theories" or Tian Yu Cao did in "The conceptual foundations and philosophical aspects of... | g9227 | [
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<p>I have a question that I can't seem to get my head around. I'm really rusty on my physics, but I'm sitting here trying to think this out, but I'm missing a really big part of the equation.</p>
<p>So lets say I have a turbine in space. It's purpose is to convert the energy given to it, in joules to watts. So I reali... | g9228 | [
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<p>Why doesn't diamond show up in X-ray imaging? Diamond is the hardest substance ever known, and as we know, X-ray radiation is produced when a cathode ray of high frequency hits a very high atomic mass target. But I am amazed: why doesn't diamond show up in X-ray imaging?</p> | g9229 | [
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<p><a href="http://en.wikipedia.org/wiki/Particle_in_a_ring" rel="nofollow">Particle in ring</a> is a well-known example where a solution of the Schrodinger equation exists. My question is: In principle we also want that $\psi'(\theta) = \psi'(\theta + 2\pi)$. The thing is that this condition is never explicitly stated... | g9230 | [
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<p>This year in college we"ve had a lot of quantum stuff thrown at us, and we"ve only been doing classical mechanics till last year. We"ve been introduced to Schrodinger"s equation, electron waves, what have you. This is my understanding(rather rudimentary) so far. When you solve Schrodinger"s equation for an atom, you... | g9231 | [
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<p>If I immerse a rod vertically in a liquid with a relative permittivity gradient (the permittivity decreases with depth), will the rod stretch (will the spacing of the atoms in the rod be affected by the varying permittivity)?</p> | g9232 | [
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<p>There was some experiment that I read about some time back in which two particles (or the same particle, but split into two) were sent in opposite directions, but when something happened to one, it happened to the other at the same moment, as if they were the same particle.</p>
<p>I thought the word for this was "e... | g9233 | [
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<p>If I have a laser light incident on the double slit at an angle O < 90 what kind of interference pattern will I see? Will i see the same with less intensity or different pattern? </p> | g9234 | [
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<p>Temperature is a measure of kinetic energy transferred to particles, henceforth, <a href="http://en.wikipedia.org/wiki/Outer_space#Environment" rel="nofollow">space</a> being vacuum, temperature cannot be measured.
But then, there is cosmic background radiation. It is the leftover heat from the Big Bang, but then he... | g9235 | [
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<p>I have a uniform electric field $E$ projected from left to right and I placed an insulator or dielectric right in the middle of it. To the left of the insulator, the $E$ is the original $E$. Inside the insulator, there is an induced field and thus the net field is less than the original. What happen to the $E$ to th... | g9236 | [
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<p>I have the following homework problem in theoretical electrodynamics:</p>
<blockquote>
<p>Show that the gauge invariant Lagrange density $\epsilon_{\mu\nu\alpha\beta} F^{\mu\nu} F^{\alpha\beta}$ can be written as a total divergence of a four-vector.</p>
</blockquote>
<p>This total divergence should be something ... | g9237 | [
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<p>Will a person on top of hill will age faster than one at sea level due to Time Dilation?</p> | g9238 | [
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<p>I'm a first year graduate student in Mathematical Physics, and I am trying to generalise a certain method involving the so-called "Differential realizations" of certain algebras. The problem I'm having is that in papers <a href="http://arxiv.org/pdf/hep-th/9810074.pdf" rel="nofollow">here</a> (Page 8) and <a href="h... | g9239 | [
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<p>All know that Inflation may solve some of the problems of the Standard Model of Cosmology and today we suppose that the field responsible for that is the inflaton. The properties of the potential $V(\varphi)$ allow via the momentum-energy tensor to define a barotropic fluid for which $$p=-\rho$$ and when the slow-ro... | g9240 | [
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<p>Ohm's Law tells us that $V = IR$. This implies that $I \propto \frac{1}{R}$. But, $R \propto l$, where l is the length of the conductor. This would mean that $I \propto \frac{1}{l}$. But this does not fit with the definition of current that says that current is the amount of charge $Q$ passing through a given point ... | g9241 | [
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<p>As our homework, we were asked to derive $P = I^2R$. </p>
<p>Now, I started off with the basic relation $P = \frac{W}{T}$. I was not able to think of anything from here, so I started plugging in random formulas from a purely algebraic point of view. </p>
<p>I tried the one for voltage $V = \frac{W}{q} \implies Vq ... | g9242 | [
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<p><img src="http://i.stack.imgur.com/H9uwm.jpg" alt="enter image description here"></p>
<p>If the above image is a cross section of a conductor, the field at the point shown is not zero. So the field inside a conductor is not zero at all points. </p>
<p>You could argue that the electrons would rearrange themselves s... | g9243 | [
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<p>Say I'm given the following Schrodinger equation</p>
<p>$$\frac{d^2u}{dx^2}+ \left[E - V(x)+ \frac{a}{x^2}\right]u(x) =0$$</p>
<p>Where $a \in \mathbb{R}$. What are the physical interpretations of this equation? I understand that it means the angular momentum is fixed, but are there any other implications associat... | g9244 | [
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<p>This is a question triggered by <a href="http://physics.stackexchange.com/questions/93124/divergent-series">this post</a></p>
<p><a href="http://en.wikipedia.org/wiki/Madelung_constant" rel="nofollow">Madelung's constant</a> is defined to the coefficient of electrostatic potential energy in a ionic crystal. In the ... | g9245 | [
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<p>While studying reflection through a plane mirror, I have been told that when the object is real the image will be virtual and <strong>the image will be real while the object is virtual</strong>.</p>
<p>What are virtual objects? Do they really exist in nature? </p> | g209 | [
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<p>If $|\psi \rangle$ represents a wavefunction through a column matrix and $\langle \psi |$ represents the dual vector in a row matrix and $|\psi \rangle \langle \psi | = \rho $ is the probability density of the wavefunction collapse to a particular value in $\mathbb{R}$ by a measurement, and matter is also a wave (De... | g9246 | [
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<p>Suppose we havean uniform slender rod of dimensions : $L$( length) and $A$( cross sectional area). Now at different points on the rod we apply different forces. So, in this situation how are we expected to find the elongation in the rod?</p>
<p>I tried in 2 different ways:</p>
<ul>
<li>I considered each part and f... | g9247 | [
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<p>In Rindler's book: Relativity, Special, General and Cosmological, is stated on page 40 that the Relativity Principle (RP), when applied to just one Inertial Frame (IF), guarantees the homogeneity and isotropy of tha IF. By inertial frame Rindler means an ideal infinity extended rigid body moving freely in a world w... | g9248 | [
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<p>Doppler redshift of distant galaxies gave first hint that the universe is expanding. I am curious to know how this redshift is actually measured and interpreted from observation. Suppose I observe some visible line say red with wavelength \lambda_1. This is not enough to tell that this line is redshifted, i.e., th... | g9249 | [
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<p>In the canonical quantization of fields, CCR is postulated as (for scalar boson field ):
$$[\phi(x),\pi(y)]=i\delta(x-y)\qquad\qquad(1)$$
in analogy with the ordinary QM commutation relation:
$$[x_i,p_j]=i\delta_{ij}\qquad\qquad(2)$$
However, using (2) we could demo the continuum feature of the spectrum of $x_i$, wh... | g9250 | [
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... |
<p>Can anyone explain the process required to make a Hadamard gate that acts on 1st, 2nd and 3rd qbits?</p>
<p>For Hgates acting on the first qubit i realise the matrix is $H=\begin{pmatrix} 1&1\\1&-1\end{pmatrix}$, but I am unsure how to formulate such a gate. As to acting on the second qubit I have read this... | g9251 | [
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<p><img src="http://i.stack.imgur.com/jHugn.png" alt="enter image description here"></p>
<p>The electric field in a wire is parallel to the wire's surface (it is always pointing "to the front"). If the electric field did not point in this direction, surface charges would build up and change the electric field to make ... | g9252 | [
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<p>A black hole engulfs the matter nearby, how does it store the mass inside? We know that matter is composed of particles, does a black hole store the mass in massive particles? Or can we assume that it's composed of extremal black holes? what are theories about it?</p>
<p>EDIT:
I checked out <a href="http://physics.... | g9253 | [
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-0... |
<p>If the Alice sends to Bob an q-bit $\alpha\left|\mathbf{0}\right> + \beta\left|\mathbf{1}\right>$ in quantum key exchange (such as BB84) it is assumed that Eve cannot copy the state (due to no cloning theorem) and attempts to read the state requires guessing the base which would allow to detect interception.</... | g9254 | [
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0.... |
<p>I know there are theories (or postulates) that hold that our Universe could be a simulation. I was wondering, if Special Relativity states that two events which are not causally linked can be judged to have happened simultaneously or not, depending on the reference frame of the observer, can someone (or something) ... | g9255 | [
0.0617162361741066,
-0.009494000114500523,
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0.0011878228979185224,
0.01102188415825367,
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0.030343344435095787,
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0.027814744040369987,
0.02191... |
<p>What sort of no-slip zone is in place when liquid water flows from a faucet through air at room temperature? Does the water drag a layer of air molecules along with it?</p> | g9256 | [
0.003686979878693819,
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0.0... |
<p>Is there a way to see that <a href="http://en.wikipedia.org/wiki/Bertrand%27s_theorem" rel="nofollow">Bertrand's theorem</a> is true intuitively. I mean without getting into too much mathematics ?</p> | g9257 | [
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0... |
<p><code>Person A</code> and <code>Person B</code> are same person (theortically). They both weigh 800N. They both can vertically
lift 1000N. They want to check something out.</p>
<p><code>G -> Gravity; N -> "Normal"; M -> Muscular active</code></p>
<p><code>R -> Netto; 1 -> Person A; 2 -> Person B... | g9258 | [
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0.03365187719464302,
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-0.02398... |
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