question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<blockquote>
<p>The block in the figure below lies on a horizontal frictionless
surface and is attached to the free end of the spring, with a spring
constant of 35 N/m. Initially, the spring is at its relaxed length and
the block is stationary at position x = 0. Then an applied force with
a constant magnitude... | g9918 | [
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<p>I'm reading about the subject of heat in a basic physics book. If I am not mistaken the formula to work out how much energy is required to increase the temperature of water is</p>
<pre><code>e = M * t * shc
</code></pre>
<p>Where </p>
<ul>
<li>e is energy in Joules </li>
<li>M is mass in kg </li>
<li>t is temper... | g9919 | [
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<p>Are there analytic solutions to the time-Dependent Schrödinger equation, or is the equation too non-linear to solve non-numerically?</p>
<p>Specifically - are there solutions to time-Dependent Schrödinger wave function for an Infinite Potential Step, both time dependent and time inpendent cases?</p>
<p>I have look... | g9920 | [
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<p>I did an experiment when I was a teenager. I want to prove/see what really went on in that experiment.</p>
<p>When taking a bath, take a warm water in bucket and start taking a bath. You will notice that the water will get cold in lets say 10 minutes. Because the water is bucket is stagnent.</p>
<p>In second insta... | g9921 | [
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<p>I know that this question has been submitted several times (especially see <a href="http://physics.stackexchange.com/questions/86116/how-are-anyons-possible">How are anyons possible?</a>), even as a byproduct of other questions, since I did not find any completely satisfactory answers, here I submit another version ... | g9922 | [
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-... |
<p>Nowadays it seems to be popular among physics educators to present Newton's first law as a definition of inertial frames and/or a statement that such frames exist. This is clearly a modern overlay. Here is Newton's original statement of the law (Motte's translation):</p>
<blockquote>
<p>Law I. Every body persever... | g637 | [
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<p>When applying DC to a neon lamp, only one electrode glows:</p>
<p><img src="http://i.stack.imgur.com/3poGs.jpg" alt="http://commons.wikimedia.org/wiki/File:Neonlamp3.JPG"> <a href="http://en.wikipedia.org/wiki/File%3aNeonlamp3.JPG">The voltages across the lamps are left: DC (left lead positive), middle: DC (right l... | g9923 | [
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<p>If I remember well, they said that it can't, but I do not know why.</p>
<p>Yes, I meant if gravity can be shielded using something like a Faraday cage
(or something else?).</p>
<p>Thank you.</p> | g9924 | [
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<p>Can a solar thermal collector common on private roofs today designed for collecting heat for the household ever collect enough heat to power a stirling engine of say this model: <a href="http://www.whispergen.com/main/achomesspecs_info/" rel="nofollow">http://www.whispergen.com/main/achomesspecs_info/</a></p>
<p>No... | g9925 | [
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0.0... |
<p>A 40-gallon electric water heater has a 10kW heating element. What will the water temperature be after 15 min of heating if the start temp is 50F degrees.</p>
<p>There must be an equation. I can't find it in notes or text.</p> | g9926 | [
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<p>I've almost finished one postdoc, and haven't found another yet. If I don't find one in time, can I keep publishing papers? I have 2 scenarios: </p>
<ol>
<li><p>If I did most of the research during the postdoc, but submit it afterwards.</p></li>
<li><p>If I start the research while I'm unemployed.</p></li>
</ol>
<... | g9927 | [
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0.0... |
<p>I tried this sight before to find filtering options and got fantastic results, so let's try again!</p>
<p>I am setting up an experiment that requires light of two different frequencies (445nm and 350nm). The light ultimately needs to be focused on a small area. I can think of two good ways to make this happen:</p... | g9928 | [
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<p>Ok, from astronomical observations we can tell that the observable matter is separating - so rewind the clock about 13.7 billion years and it was all at a single point.</p>
<p>However, how do we distinguish between the following two options: </p>
<ol>
<li>Universe is expanding </li>
<li>Matter distribution is in... | g9929 | [
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... |
<p>Why is a wine glass shaped the way it is? And why are there different shapes for different wines? Is this a tradition, or is there any scientific reason behind it?</p> | g9930 | [
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<p>I'm trying to understand something I've observed in exposing LaAlO3 substrates to an oxygen plasma (yielding atomic oxygen). In literature, these substrates are frequently "cleaned" in a oxygen rich environment by exposing the surface to atomic oxygen (via plasma source) at substrate temperatures greater than 700 C... | g9931 | [
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<p>I'm working through Polchinski's book on string theory, and I ran into something that I don't think I understand. I'm hoping that someone who knows this stuff can help me out.</p>
<p>Before calculating the Dp-brane tension in Chapter 8, Polchinski says that we could have obtained the same result by calculating the ... | g9932 | [
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<p>According to Einstein, do observers in relative motion agree on the time order of all events?</p>
<p>I don't think they would agree on the timing of events, but I am having trouble figuring out why they wouldn't agree. Any thoughts?</p> | g9933 | [
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<p>Two fundamental equations regarding <a href="http://en.wikipedia.org/wiki/Wave-particle_duality" rel="nofollow">wave-particle duality</a> are:
$$ \lambda = \frac{h}{p},
\\
\nu = E/h .$$</p>
<p>We talk about <a href="http://en.wikipedia.org/wiki/De_Broglie_wavelength" rel="nofollow">de Broglie wavelength</a>, is it ... | g9934 | [
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<p>I was looking at the <a href="http://en.wikipedia.org/wiki/Isotopes_of_technetium" rel="nofollow">isotopes of technetium</a> page on Wikipedia recently, and it seems that the metastable ${^{95m}Tc}$ has a substantially longer half-life (61d) than its most stable state of ${^{95}Tc}$ (20h). Several alternative sourc... | g9935 | [
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<p>Kind of a weird question compared to what I normally ask on here, but I've been wondering about this for a while.</p>
<p>Does the LHC beam generate any photons within the visible light spectrum? Assuming the beam was traveling through air instead of a vacuum, would it interact with the nitrogen or oxygen to genera... | g9936 | [
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<p>In a standing wave, how does energy travel past a node?</p>
<p>It should just get reflected. Assume the case of first overtone and you strike the string at a place. How will energy distribute itself?</p>
<p>If it distributes over the whole string, then how is it the wave traveled past a node?</p>
<p>Basically the... | g9937 | [
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<p>I heard that the moon is moving away from the Earth gradually.</p>
<p>Will it escape at some point?</p> | g317 | [
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<p>I want to be able to find the Wigner transforms of operators of the form $\Theta(\hat{O})$, where $\Theta$ is the Heaviside function and $\hat{O}$ in general depends on both $x$ and $p$. For the operators of interest, $\tilde{O}$ is known. Since the Wigner transform is linear, I can use the expression $$ \Theta(x)=\... | g9938 | [
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<p>According to my textbook, if a square loop with mass $M$ is allowed to free fall (with a magnetic field at the bottom side and as soon as the square loop is dropped then the area inside the loop begins to be filled with more and more magnetic field) through a magnetic field, it will reach a terminal velocity. This i... | g9939 | [
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<p>I have some doubts about the next excercise:</p>
<blockquote>
<p><em>A bar of length $2a$ and mass $m$ moves freely with both of its extremes on a ring of radius $\sqrt2a$. The ring can rotate freely in a certain diameter, remaining the center fix. Find the equations of motion.</em></p>
</blockquote>
<p>I did it... | g9940 | [
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<p>Intuitively to me it seems likes increasing compression ratio would require more work to compress the gasses before ignition, so you'd just end up getting back what you put in - like a spring. What am I missing?</p> | g9941 | [
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<p>Is there a difference between a half skyrmion and a meron? I'm asking this in regard to half skyrmion theories of High Tc Superconductors. It would be interresting to know if the proposed half skyrmions which emerge in the disturbed antiferromagnetic spin structure are actually merons.</p> | g9942 | [
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<p>My QM book says that when two observables are compatible, then the order in which we carry out measurements is irrelevant.</p>
<p>When you carry out a measurement corresponding to an operator $A$, the probability that the system ends up in the eigenvector $\psi_n$ is
$$P_n ~=~ \frac{|<\psi|\psi_n>|^2}{<\p... | g9943 | [
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<p>I need to find when the sun reaches the Zenith at a given latitude.</p>
<p>What I've done so far:</p>
<p>$L=23.5 \cdot \sin(\frac{2\pi}{365.25}\cdot D) $</p>
<p>Here L is the latitude (<23.5) and D is number of days from March 21.</p>
<p>This is based on my understanding that the sun executes SHM around the c... | g9944 | [
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<p>Which textbook in Electrodynamics which emphasizes practical applications and real life examples would you recommend for undergraduates?</p> | g271 | [
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<p>The path integral provides a method for computing a time evolution by a weighted summing up all possible deviations. </p>
<p>Is there such a method for a system, where one not only knows the initial condition, but also how the system end up? I.e. given is the beginning and the end configuration and what one is inte... | g9945 | [
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-0.00... |
<p>What keeps it from falling into the center if not angular momentum?</p> | g9946 | [
0.06458576768636703,
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<p>Timbre is a property associated with the shape of a sound wave, that is, the coefficients of the discrete Fourier transform of the corresponding signal. This is why a violin and a piano can each play the same note at the same frequency yet sound completely different. Now for light: if you mix red and blue light, the... | g9947 | [
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0.052... |
<p>I have recently started learning about tensors during my course on Special Relativity. I am struggling to gain an intuitive idea for invariant, contravariant and covariant quantities. In my book, invariant quantities are described as being those physical quantities associated with a point in space e.g. temperature... | g9948 | [
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0.03741666302084923,
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0.07617516070604324,
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<p>Let us imagine a free, negatively charged object that is in rest and placed in an elecric field of a point positive charge. The positive charge has a huge mass and cannot move, so we consider only the movement of the negative charge. The negative charge starts falling the center at time t0. </p>
<p>It is straight f... | g9949 | [
0.07426603138446808,
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<blockquote>
<p><em>A particle A decays into particles B, C and D. The spin of A, B and C particles is 1/2 each. What are the possible spins of particle D?</em></p>
</blockquote>
<p>My attempt is the following:</p>
<p>Since B and C have spin 1/2 each, these can form singlet or a triplet. So the spin of D can only b... | g9950 | [
0.019359752535820007,
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/23028/proof-that-the-one-dimensional-simple-harmonic-oscillator-is-non-degenerate">Proof that the One-Dimensional Simple Harmonic Oscillator is Non-Degenerate?</a> </p>
</blockquote>
<p>I'm trying to con... | g318 | [
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0.... |
<p>Perhaps I have missed something in my notes, but I have noticed when looking at different sources that some textbooks/sites state that the fringe brightness for the young's experiment is the same for all the bright fringes. Others, say that the brightness "falls off" with angle theta. Well, which is it? And how do y... | g9951 | [
0.019041981548070908,
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0.02894... |
<p>The Einstein Field Equations emerge when applying the principle of least action to the Einstein-Hilbert action, and from what I understand the path integral formulation generalizes the principle of least action. What happens when you apply the path integral instead of the action principle to the Einstein-Hilbert act... | g9952 | [
0.025618210434913635,
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<p>In the famous <a href="http://prola.aps.org/abstract/PR/v73/i7/p803_1" rel="nofollow">Alpher-Bethe-Gamow paper</a>, the authors say: "it is necessary to assume the integral of $\sigma_n dt$ during the building-up period is equal to $5 \times 10^4 \frac{\text{g sec}}{\text{cm}^3}$"</p>
<p>How do they determine this ... | g9953 | [
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0.03715291619300842,
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0.003818322904407978,
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0.05526861175894737,
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<p>It seems to me that extra gravitational potential energy is created as the universe expands and the distance between massive objects such as galaxy clusters increases; this implies that energy is not conserved in the universe. Is that right?</p> | g9954 | [
0.05659632384777069,
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<p>The Hamiltonian is traditionally defined as
\begin{align}
H_{\text{flat}} = U^{\dagger}DU
\end{align}
where $D$ is a diagonal matrix with real eigenvalues and $U^{\dagger}U=I$ are the unitary transformations to generalize $H_{\text{flat}}$ in any traditional base. Thus the hermitian relation $(H_{\text{flat}})^{\da... | g9955 | [
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0.0... |
<p>I was reading <a href="http://science.nasa.gov/science-news/science-at-nasa/2003/09sep_blackholesounds/">this article</a> from NASA -- it's <em>NASA</em> -- and literally found myself perplexed. The article describes the discovery that black holes emit a "note" that has physical ramifications on the detritus around ... | g9956 | [
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<p>How the proton state is found and renormalized in lattice QCD? Is there any literature shows the method step by step? What about other bound states in QCD if we somehow know their quantum numbers?</p> | g9957 | [
0.044950637966394424,
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<p>I'm stuck on a problem that I found in a book (Modern Thermodynamic with Statistical Mechanics, Helrich S., problem 5.2).</p>
<p>The text of the problem is that:</p>
<blockquote>
<p>Consider a solid material for which:</p>
<p>$$
\frac{1}{\kappa_T} = \frac{\varepsilon}{2V_0}\left[\frac{2\Gamma c_v T}{\vareps... | g9958 | [
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0.016696587204933167,
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0.0010045426897704601... |
<p>I have been working on a problem about finding the electrostatic potential energy stored on a capacitor of concentric spheres with inner radius $a$ and outer radius $b$ and with charge $Q$. I've got to first calculate the energy using the capacitance and then integrating the energy density. </p>
<p>I did the follow... | g9959 | [
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0.03072177618741989,
0.021234197542071342,
0.021301504224538803,
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0.03994303196668625,
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0.015120396390557289,
0.003610034938901663,
-0.0... |
<p>This comes from an AP review packet. I'm given a potential energy functon, $$U(r)=br^{-3/2} + c,$$ where $b$ and $c$ are constants, and need to find the expression for the force on the particle.</p>
<p>There's a graph of $U(r)$ given with the problem, but I'm not sure if it's needed or not. I'm just looking for h... | g9960 | [
0.021162837743759155,
0.04546724259853363,
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0.035919103771448135,
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0.014260179363191128,
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0.011158578097820282,
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0.042087506502866745,
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<p>I didn't see this listed on the books page so here it is. I'm currently in an introductory Solid State course, and we are using Kittel's book. I have been having a rough time with this book although I am starting to get used to it as we get farther in. What are good introductory solid state books?</p> | g9961 | [
0.046624381095170975,
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0.024158824235200882,
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<p>Recently I realized the concept of center of mass makes sense in special relativity. Maybe it's explained in the textbooks, but I missed it. However, there's a puzzle regarding the zero mass case</p>
<p>Consider any (classical) relativistic system e.g. a relativistic field theory. Its state can be characterized by ... | g9962 | [
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0.0034539944026619196,
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... |
<p>The scenario:</p>
<p>A ray of light strikes the center of the (a) flat surface and (b) curved surface of a semicircular glass medium with the angle of incidences in degrees of 10, 20, 30, 40 and 50. </p>
<p>The angles of refraction for each angle of incidence and for each surface were:</p>
<p>(a) flat surface</p>... | g9963 | [
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<p>Bell's inequality theorem, along with experimental evidence, shows that we cannot have both realism and locality. While I don't fully understand it, Leggett's inequality takes this a step further and shows that we can't even have non-local realism theories. Apparently there are some hidden variable theories that g... | g788 | [
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0.004440023098140955,
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0.02978839911520481,
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<p>About two years ago I posted a question about a symmetrical twin paradox: <a href="http://physics.stackexchange.com/questions/361/symmetrical-twin-paradox/43803#43803">Here</a>.</p>
<p>Recently a new answer was posted and an intense discussion ensued: <a href="http://physics.stackexchange.com/a/43803/171">Here</a>.... | g9964 | [
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0.05116841197013855,
0.0021928853821009398,
0.05581989511847496,
... |
<p>The title question would be too long if I tried to specify it clearly. So let me be more clear. Consider the class of theories having the following properties:</p>
<ol>
<li>The langrangian density is only dependent of scalars created from the curvature tensors (for example $R, R^{ab}R_{ab}, R^{abcd}R_{abcd}, C^{a... | g9965 | [
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0.023187821730971336,
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-0.00... |
<p>I was wondering how far in imaging physics had gotten. Do we hold the technology to actually take a picture of, say, an alpha particle, or even a single atom?</p>
<p>I realise we aren't talking about camera pictures, so what kind of imaging techniques have taken images/is most likely to be the technique to take an ... | g733 | [
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<p>I know the concept behind String Theory. But I was wondering if anyone knows of a good place to start learning more about the theoretical physics behind it? Maybe a book someone can recommend to me! I have a strong mathematical background, so something abstract is fine for me. I also know quite a bit about physics.<... | g319 | [
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0.012988... |
<p>It is known that the classical equation of motion for a scalar field wave packet on a curved spacetime background gives the geodesic trajectory (the e.o.m. is $(\nabla_\mu \nabla^\mu + m^2) \Phi=0$). However, I couldn't see that. </p>
<p>How can one derived the geodesic equation from the above e.o.m. ?</p> | g9966 | [
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<p><strong>If I had an infinite number of sine waves with frequencies between 0 and 2, and I know what amplitude each wave has, is there a way for me to predict how they interfere?</strong></p>
<p><strong>for example if I have:</strong></p>
<p>frequencies=[ 0 ......................... 2]</p>
<p>amplitudes=sin(freque... | g9967 | [
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0.015461022034287453,
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<p>Consider two places next to each other: Place 1, where there is a gravitational field whereas Place 2 - there's no field.</p>
<p>Now if we lifted a box in place 1, it gains potential energy. Then, we move this box horizontally to place 2. What happens to this energy?</p> | g9968 | [
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0.0014451692113652825,
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<p>An accelerated clock will measure a smaller elapsed time between two events than that measured by a non-accelerated (inertial) clock between the same two events.</p>
<p>. <img src="http://www.outersecrets.com/real/image/rsri.gif" alt="Valid XHTML"></p>
<p><strong>Experiment #1</strong>
Imagine that you have... | g9969 | [
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0.011230096220970154,
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0.0... |
<p>In an introductory Quantum Mechanics textbook, I found the following statement:</p>
<blockquote>
<p>For two Hamiltonians $H$ and $H'$, non commuting with each other, but commuting with the same group of translations ${\cal{T}} (\vec{R})$ an eigenvector of $H$ can't be an eigenvector of $H'$.</p>
</blockquote>
<p... | g9970 | [
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0.049262721091508865,
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0.02931700460612774,
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0... |
<p>The source S sends a photon into the beam splitter below.
There is a 50% chance that it will be detected at A and a 50% chance it will be detected at B.</p>
<pre><code>S -----------\---------> A
|
|
|
v
B
</code></pre>
<p>Now if we assume that phy... | g9971 | [
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0.044375013560056686,
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-0.... |
<p>We know from fermat's principle that light follows the smallest path. But how light know that which path is smallest?</p> | g9972 | [
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<p>What would happen if I take a glass of water in space i.e. outside the gravitational influence of earth?
My teacher said that the water would vaporize but I am not completely satisfied by the answer.
I feel that it will still be in the glass because of adhesion forces.
Am I correct?</p> | g9973 | [
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0.04007990285754204,
0.01374130416661501,
-0.01068601943552494,
-0.06895627826452255,
0.07596749812364578,
-0.044108983129262924,
0.007057759445160627,
-0.003133037593215704,
-0.027328945696353912,
0.049959488213062286,
0.05346100404858589,
-0.00004422240817802958,
0.... |
<p>While reading "<a href="http://en.wikipedia.org/wiki/Surface_plasmon_resonance" rel="nofollow">Surface Plasmon Resonance</a>," I came across the following:</p>
<blockquote>
<p>"The resonance condition is established when the frequency of light photons matches the natural frequency of surface electrons oscillating... | g9974 | [
0.052107881754636765,
0.027788620442152023,
0.0006046821363270283,
0.012481908313930035,
0.05820997431874275,
0.025237511843442917,
-0.059559401124715805,
0.010098847560584545,
0.05167923495173454,
-0.0391998328268528,
0.016375135630369186,
0.02372470311820507,
-0.02543146163225174,
0.0085... |
<p>When considering <a href="http://en.wikipedia.org/wiki/Reaction_diffusion_equation">diffusion of chemicals</a>, the reaction part is business of <a href="http://en.wikipedia.org/wiki/Chemical_kinetics">chemical kinetics</a>, where the relevant characteristics of different substances come from <a href="http://en.wiki... | g9975 | [
0.012718480080366135,
0.0030129416845738888,
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0.03257878124713898,
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0.007806973531842232,
0.05037010461091995,
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0.011664312332868576,
0.016443610191345215,
0.005350443068891764,
0.0719020739197731,
0.00... |
<p>Can anyone provie me the proof of $Dq-qD=1$ where $D=\frac{\partial }{\partial q}$ refers to the differential operator?</p>
<p>Or if it's something special to quantum mechanics, why is it?</p>
<p>Is this following from $[\hat{q},\hat{p}] =i\hbar ~{\bf 1}$?</p> | g9976 | [
0.04992573708295822,
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0.... |
<p>We know that when we speak sound waves are created. The air particles compress and rarefy and pressure is more at the nodes and less at anti-nodes. But can we say the same thing about waves on a string,- that pressure is more at the nodes than the anti-nodes? </p> | g9977 | [
0.03180207312107086,
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0.005419967696070671,
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0.1285254955291748,
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-0.02528284676373005,
-0.03658973053097725,
0.03892940655350685,
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0.0... |
<p>How will we find $V_{ab}$ when $\vec E = (2i+3j+4k)$ <strong>N/C</strong> , $\vec R_a = (i-2j+k)$ <strong>m</strong> and $\vec R_b = (2i+j-2k)$ <strong>m</strong> ?
I know $\vec E= -\frac{d V}{d\vec r}$, but I don't know what should be my initial approach toward the question.</p> | g9978 | [
0.028569553047418594,
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0.01213014218956232,
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0.04650108888745308,
0.029838064685463905,
0.01886... |
<p>According to my understanding of SR, if I travel at 0.8c relative to a line of clocks, I should see the clocks in front of me going 3 times faster than my own, and those behind me going 3 times slower than my own (Doppler effect).
OK, so what happens at my exact location? I reckon that as I look nearer and nearer t... | g9979 | [
0.027116769924759865,
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0.0727102980017662,
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0.062117379158735275,
0.009866798296570778,
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0.007754597347229719,
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<p>A few days ago, I happened to go through the chapters on Radiation, and Photometry, studying them at quite an elementary level. I studied Wien's displacement law, and the dependence of luminous flux of a radiant source on the total radiant flux of the source, and the wavelength distribution. From studying them, I th... | g9980 | [
-0.020779140293598175,
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0.024499064311385155,
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0.04030323401093483,
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0.012864532880485058,
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0.03952816501259804,
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0.... |
<p>I would like to understand why is it the charge density while dealing with currents is $\mathop{\mathrm{div}}(E)/4\pi$, while when dealing with insulators is $-\mathop{\mathrm{div}}(E)/4\pi$?</p>
<p>Thank you very much, and sorry if it's too obvious.</p> | g9981 | [
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0.03271084278821945,
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0.020103882998228073,
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-0... |
<p>I'm always quite curious about the "Energy cube" in <a href="http://en.wikipedia.org/wiki/Transformers" rel="nofollow">Transformers</a>, or namely <a href="http://tfwiki.net/wiki/Energon_cube" rel="nofollow">Energon</a>. </p>
<p>Is it really possible to store energy, such as electricity, into such a compact form? s... | g9982 | [
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<p>I'm trying to understand the definition of the n-th order correlation function. My aim is to translate the math into a numerical implementation in order to compute the correlation function $g^{(n)}$ for a distribution of spherical particles with $n=\lbrace3,4,5,\ldots\rbrace$. </p>
<p>I'm going to present you what ... | g9983 | [
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<p>I have just read (in the black holes chapter 14 on p244 of <a href="http://rads.stackoverflow.com/amzn/click/0071498702" rel="nofollow">this</a> book Ref.1) that in string theory, when one adds an (electric?) charge $Q$ to a static black hole, one can arrive at an exotic supersymmetric black hole.
This sentence is n... | g9984 | [
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0.007303737103939056,
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<p>In probability theory, the Fokker-Planck equations governs the trajectory of a sample path of a stochastic process -- say the heat equation in the case of a Wiener process.</p>
<p>Consider a Gaussian wave-function evolved with respect to the free-Hamiltonian -- for the sake of simplicity it may be a one dimensional... | g9985 | [
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0.002851190511137247,
0.0049356571398675... |
<p>Here's my reasoning... time dilation due to velocity: t'=t√(1-v^2) v expressed as a % of the speed of light. If you are moving through distance at the speed of light, to an observer at rest relative to you, zero time has elapsed. So if you are at complete rest (no particle movement at all) is infinite time elapsing... | g9986 | [
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<p>I was on a commercial flight in a 737 stationary at idle on a taxiway. It had recently stopped raining so the relative humidity was likely near 100% and the air temperature was about "light jacket" level. I was in a window seat forward of the engine intake so I could see the whole intake.</p>
<p>Every 30 seconds or... | g9987 | [
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0.00822371430695057,
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0.014415229670703411,
0.06924603134393692,
0.0... |
<p><a href="http://en.wikipedia.org/wiki/Gravitational_wave" rel="nofollow">Gravitational waves</a> propagate through a medium of space-time. Are they traverse waves or longitudinal waves? Or do they propagate without oscillating?</p> | g320 | [
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<p>Take the Poincaré group for example. The conservation of rest-mass $m_0$ is generated by the invariance with respect to $p^2 = -\partial_\mu\partial^\mu$. Now if one simply claims</p>
<blockquote>
<p>The state where the expectation value of a symmetry generator equals the conserved quantity must be stationary</p>... | g9988 | [
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0... |
<p>Cross-posted to Math.SE <a href="http://math.stackexchange.com/q/487525/">here</a>. </p>
<p>Physicists are widely respected for using and sometimes even inventing mathematics yet physicists study Physics which is a subject in its own right.</p>
<p>So surely someone studying physics spends less time studying maths ... | g9989 | [
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<p>Assuming no air resistance etc, how long is the ball in the air for?</p>
<p>This is actually part of a longer question concerning the ball trajectory on different planets but I think there must be an easier way than what I am doing. </p>
<p>This is what I have -
$$Y -Direction$$ $$v_y=u_y+a_yt$$
$$0=u_y-9.8t$$
$$... | g9990 | [
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0.08206386119127274,
0.029117055237293243,
-... |
<p>As previously learnt that increasing the doping will decrease the width of the depletion layer and vice-versa. However, I am unable to understand this. Does it have some relation with force of repulsion?</p> | g9991 | [
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<p><a href="http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/" rel="nofollow">"Photons act like they go through two paths, even when we know which they took".</a></p>
<p>Please refer the above link and its conclusion.</p>
<p>I am an Engineer. What I infer fr... | g9992 | [
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0.018795110285282135,
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0.0397... |
<p>Is it possible to show that ${\gamma^5}^\dagger = \gamma^5$, where
$$ \gamma^5 := i\gamma^0 \gamma^1 \gamma^2 \gamma^3,$$
using only the anticommutation relations between the $\gamma$ matrices,
$$ \left\{\gamma^\mu,\,\gamma^\nu\right\}=2\eta^{\mu\nu}\,\mathbb{1},$$
and <em>without</em> using any specific representat... | g9993 | [
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0.010174635797739029,
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0.059847038239240646,
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... |
<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Torque">torque</a> and <a href="http://en.wikipedia.org/wiki/Moment_%28physics%29">moment</a>? I would like to see mathematical definitions for both quantities.</p>
<p>I also do not prefer definitions like "It is the tendancy..../It is a measure o... | g9994 | [
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<p>We know that photons are the antiparticles of themselves and if they interact with each other through higher order process do they annihilate and again produce photons?</p>
<p><a href="http://physics.stackexchange.com/q/54323/2451">Here</a> is the Phys.SE question that made me ask this question.</p> | g9995 | [
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<p>I sometimes hear stories where people compare their feelings in winter in different places in the world.</p>
<p>It goes like</p>
<blockquote>
<p>in city X the temperature was the same as in city Y, but the humidity made me feel much colder...</p>
</blockquote>
<p>or </p>
<blockquote>
<p>oh well, -20°C would ... | g9996 | [
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-0.00727824354544282,
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0.010305158793926239,
0.003945935517549515,
0.00... |
<p>I was wondering about the relation between noise with distance, assuming a point source, using sound as the method for communication and air as the medium of communication. Obviously as the distance from the sound source increases, noise should increase- but what is the nature of this relationship? Is it linear or n... | g9997 | [
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0.013843892142176628,
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0.008672540076076984,
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0.05355853587388992,
0.0... |
<p>There are a number of possible symmetries in fundamental physics, such as:</p>
<ul>
<li><p>Lorentz invariance (or actually, Poincaré invariance, which can itself be broken down into translation invariance and Lorentz invariance proper),</p></li>
<li><p>conformal invariance (i.e., scale invariance, invariance by hom... | g9998 | [
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0.04951940104365349,
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0.006895152851939201,
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... |
<p>This text in my book is pretty confusing:<sub>With my emphasis</sub></p>
<blockquote>
<p>A simple pendulum is a <em>heavy point mass</em> (bob) suspended from a rigid support by a <em>massless and inextensible string</em>. This is an ideal case because <strong>we cannot have</strong> a <em>heavy mass having the s... | g9999 | [
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<p>I'm a high school teacher trying to teach my students (15year olds) about refraction. I've seen a lot of good analogies to explain why the light changes direction, like the marching band analogy, that the light "choose" the fastest way etcetc, and for most of my students these are satisfying ways to explain the phen... | g10000 | [
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0.05792... |
<p>If you put a latex balloon in a vacuum, how much would it expand? And would it pop? Assume it doesn't leak.</p>
<p>EDIT:</p>
<p>Some numbers: Ambient pressure is 100 KPa, balloon is perfectly spherical with a diameter of 300 mm, deflated it has a diameter of 25mm, temperature is always at equilibrium.</p>
<p>Ques... | g10001 | [
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<p>Is it possible that some parts of the universe contain antimatter whose atoms have nuclei made of antiprotons and antineutrons, sorrounded by antiprotons? If yes what can be the ways to detect this condition without actually going there? Or can we detect these antiatoms by identifying the light they emit as composed... | g321 | [
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0.014... |
<p>Many years ago, a discrepancy was found between the experimentally measured value of the <a href="http://en.wikipedia.org/wiki/Anomalous_magnetic_dipole_moment">muon magnetic moment</a>, and the theoretically calculated value. Shockingly, most physicists were blase about it. It was no big deal to them. They dismisse... | g10002 | [
-0.004978938028216362,
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... |
<p>I'm intrigued by this, and how it would work:- 3 sub-questions if I may:</p>
<ol>
<li><p>Construction:
As I understand it's a flexible sphere constrained by a rigid edge.</p>
<p>a. Do we simply glue 2 flat circular pieces of flexible material together at the edges and inflate? (e.g. the <a href="http://www.qsl.n... | g10003 | [
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0.00878150481730699... |
<p>I have just started learning QFT. I have just completed scalar fields, which I learnt in using Canonical Quantisation and Path integrals. I did calculation of Casimir force between two metal plates using just free scalar field theory (using the vacuum energy). However, I am not able to find a way to do this thing us... | g10004 | [
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<p>It is possible that the universe has naturally a slight curve of spacetime, even in a place where there is not a massive object, and that this curve is responsible for the perception of the relative velocity between two bodies? For example: The body A and body B, has as its starting point the C point and arrival poi... | g10005 | [
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0.027... |
<p>I've been struggling with the concepts of these three terms - Fermi Energy, Fermi Level and work fuction. Now, I was given these definitions (in the context of semi-conductors):</p>
<ul>
<li>Fermi Level is the energy where at $0\rm K$, all energy levels below it are occupied and all energy levels above it are empty... | g10006 | [
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<p>Compare the number of scattered particles:<br>
$N_s=Fa\int\sigma(\theta)d\Omega$<br>
With the total number of incident particles:<br>
$N_{in}=Fa$</p>
<p>Here, F is the flux of incoming beam, a the area. sigma the crossection and omega the solid angle.</p>
<p>Why isnt $N_s=N_{in}$?
How does one define which partic... | g10007 | [
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0.014... |
<p>It would seem that <a href="http://en.wikipedia.org/wiki/Planck%27s_law" rel="nofollow">Planck's law</a> implies that objects of similar radiation spectra have the same temperature if the objects are "similarly close" to being <a href="http://en.wikipedia.org/wiki/Black_body" rel="nofollow">black bodies</a>.</p>
<p... | g10008 | [
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0.0... |
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