question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
|---|---|---|
<p>Say that a closed system has $n$ dimensions and is in the shape of a $n$-ball with a radius of 1, it's volume will be</p>
<p>$$\frac{\pi^\frac{n}{2}}{\Gamma(\frac{n}{2}+1)}$$</p>
<p>which tends to 0 yet is not empty as n tends to infinity.</p>
<p>My question might not make any sense, and my understanding of entro... | g12215 | [
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<p>I have a problem with understanding of these sentences:</p>
<blockquote>
<p>We have indicated in the opening paragraph of the Introduction that surface plasmon polaritons are solutions
of Maxwell’s equations in which the effects of retardation—the finiteness of the speed of light—are
taken into account. An im... | g12216 | [
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<p>I understand that one can measure a single photon being absorbed using a photomultiplier tube or CCD.</p>
<p>Can one measure a single photon being <em>emitted</em> by monitoring the current through an LED or the recoil of an emitting ion?</p>
<p>Is it therefore possible to detect the same photon both being emitted... | g12217 | [
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<p>Can <a href="http://en.wikipedia.org/w/index.php?title=Template%3aTheories_of_gravitation&oldid=558771017" rel="nofollow">this template at Wikipedia</a> be true? It seems to suggest that <a href="http://en.wikipedia.org/wiki/Einstein%E2%80%93Cartan_theory" rel="nofollow">Einstein-Cartan theory</a>, <a href="http... | g12218 | [
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<p>Q: When does the wavefunction collapse? A: When a measurement is made. But when exactly is this? I have a question about the time at which a measurement can be considered to have occurred: what exactly constitutes a measurement?</p>
<p>Consider the following experiment: A beam of spin $½$ particles of well defined... | g12219 | [
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<p>"Even if a magnet is broken into atoms, each atom shall be a complete magnet. If the atom is further broken into electrons, protons, neutrons, etc. even then each particle shall behave like a complete magnet." </p> | g12220 | [
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<p>Gravitational force is mediated by graviton exchange. If I am standing outside a black hole, I can of course feel the attracting force towards the black hole. This should correspond to gravitons mediated between the matter inside the horizon and myself; but then these gravitons should cross the horizon from the insi... | g215 | [
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<p>We all know that gravity decreases as we go upward, we also know that gravity decreases as we go inside the earth? I don't know why gravity decreases as we go downward or inside the Earth? Please explain? </p> | g50 | [
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<p>Your goal is to complete your 10,000-m run in less than 30.0 min. Apparently you've started too slowly because at 27.0 min, you still have 1100 m to go!
Part A You can accelerate at 0.20 m/s2. For how many seconds should you accelerate (and after this have constant velocity) in order to complete the run on time? ... | g12221 | [
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<p>We all know that sound sensation is produced only when sound waves reach upto us. We all know that sound waves are disturbances propagating in air, Vibration is necessary for the generation of sound, but it always forces me to ponder that how was it known or deduced that vibration is necessary for any form of sound... | g12222 | [
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<p>In a paper, I ran into the following definition of the zero point fluctuation of our favorite toy, the harmonic oscillator:
$$x_{ZPF} = \sqrt{\frac{\hbar}{2m\Omega}} $$
where m is its mass and $\Omega$ its natural frequency.
However, when I try to derive it with simple arguments, I think of the equality:
$$E = \frac... | g12223 | [
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<p>We know the escape velocity from the Earth is 11.2km/s. Isn't it the velocity required to escape from earth if we go normal to the surface of earth? i.e while we derive the formula for the escape velocity from earth we never consider the slanted motion of the object. So when we launch a rocket we need to use very le... | g12224 | [
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<p>I want to learn how to construct spaces of quantum states of systems.</p>
<p>As an exercize, I tried to build the space of states and to find hamiltonian spectrum of the quantum system whose Hamiltonian is the Hamiltonian of the harmonic oscillator with the quadratic term: $\hat{H}=\hat{H}_{0}+\hat{H}_{1}$, where<... | g12225 | [
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<p>For a report I'm writing on Quantum Computing, I'm interested in understanding a little about this famous equation. I'm an undergraduate student of math, so I can bear some formalism in the explanation. However I'm not so stupid to think I can understand this landmark without some years of physics. I'll just be happ... | g12226 | [
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<p>I've heard an explanation for this, and my professor wasn't really able to clarify my questions, so I was hoping someone could help:</p>
<p>Suppose there is an electrostatic field $\vec{E_{net}}\ne\vec{0}$, then the electrons on/in the conductor would be free to move, and then $\vec{E}_{net}$ wouldn't be an electro... | g12227 | [
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<p>What is the difference of work $W$ and thermal energy $Q$ in thermodynamic <a href="http://en.wikipedia.org/wiki/Stirling_cycle" rel="nofollow">Stirling-process</a> (in simple form) for ideal gas?</p>
<p>I think that you need work to preserve this process and you bring thermal energy so that temperature $T$ rises i... | g12228 | [
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<p>Why laundry dry up also in cold/frost? When you have frost, water in the clothes should freeze, but if clothes are dry, then it should be possible that steam in the clothes does not have time to freeze.</p> | g12229 | [
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<p>I'd like to know if there have been attempts in solving the full problem of the dynamics of a classical hydrogen atom.</p>
<p>Taking into account Newton equations for the electron and the proton and Maxwell equations for the electromagnetic field produced by these charges one obtains a higly non-linear set of coupl... | g626 | [
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<p>With the approaching <a href="https://en.wikipedia.org/wiki/Hurricane_Sandy" rel="nofollow">hurricane</a>, I am curious about what would happen if I go outside, in particular whether the wind gusts might be fast enough to blow me away. How fast would the wind have to be to blow away a person?</p> | g12230 | [
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<p><img src="http://hyperphysics.phy-astr.gsu.edu/hbase/particles/imgpar/pidec1.gif" alt="Pion Plus Decay"></p>
<p>Since the charged pions decay into two particles, a muon and a muon neutrino, seems quarks disappeared!,</p>
<p>The decay proceeds by the weak interaction $W^{+}$ and can be visualized in terms of Feynma... | g12231 | [
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<p>I am trying to work out the steps of the proof of the expression: $$\sum_n (\mathcal{E_n}-\mathcal{E_s})|\langle n|e^{i\mathbf{q}\cdot\mathbf{r}}|s \rangle|^2 = \frac{\hbar^2q^2}{2m}$$ from Eq. (5.48) in the book <em>Principles of the Theory of Solids</em> by Ziman. In the book it is mentioned that this can be shown... | g12232 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/937/how-does-gravity-escape-a-black-hole">How does gravity escape a black hole?</a> </p>
</blockquote>
<p>If nothing in the universe can travel faster than light, how come light can't escape a black hole... | g215 | [
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<p>If a stone is launched upward, of which is subject to gravity and air resistance, which of the following will have a greater kinetic energy? The stone at a point on its way up, or the stone at the same point on its way down?</p>
<p>I know $KE=1/2mv^2$, and $PE=mgy$.</p>
<p>If I had to guess I would say the kineti... | g12233 | [
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<p>{..everything that follows is in the domain of relativistic kinematics..}</p>
<p>Say a particle A collides with a particle B at rest and produces particles C and D. </p>
<p>What exactly is the definition of "threshold energy" for a reaction ? </p>
<p>Is it the energy that A should have so that so that the heavier... | g12234 | [
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<p>Are there any references that present the explicit variation of the Hilbert-Einstein action plus the Hawking-Gibbons-York boundary term, and demonstrate the cancellation of the normal derivatives of metric variations? I have tried to read the original papers by York and Gibbons&Hawking, but they are not that ped... | g12235 | [
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<p>Is it possible to formulate classical electrodynamics (in the sense of deriving Maxwell's equations) from a least-action principle, without the use of potentials? That is, is there a lagrangian which depends only on the electric and magnetic fields and which will have Maxwell's equations as its Euler-Lagrange equati... | g12236 | [
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<p>As far as I see from wiki, 'consumer'-grade(non-cryogenic) thermal imaging cameras use microbolometer sensors to get integrated IR intensity over some 5-12um range. But I had an impression, that having just integrated IR intensity you can't get surface temperature precisely, especially with 0.1C precision we see on ... | g12237 | [
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<p>Does electric field caused by time varying magnetic field form closed loops(electric field starts from a positive charge and ends at a negative charge)? and are they conservative or non-conservative fields?</p> | g12238 | [
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<p>I was going to buy this add on, as I almost exclusively use my sunglasses for driving. I'm just stacking them over my normal ones now... but it's quite annoying that I almost paid the extra $$$ for this feature. Found out at the last second, luckily.</p> | g12239 | [
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<p>I am trying to derive the equation for buoyancy frequency in a stratified fluid and am struggling with some of the equations. I have a limited background in fluid dynamics so I basically just need someone to break down the continuity equation for me, in terms that are easily understood.</p>
<p>From the set of notes... | g12240 | [
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<p>Two concentric rings dielectrics and uniformly charged are suspended on the same floor.</p>
<p>The outer ring has a radius R and mass M,
while the other has radius r << R and mass M.</p>
<p>The outer ring that has overall charge Q,
is made to rotate around the axis passing through the center and perpendicu... | g12241 | [
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<p>It is known that molecules at the surface are strongly attached to each other (more attraction less repulsion) than those within the bulk attraction and repulsion are balanced). This is the molecular description of the surface tension and its net direction i.e., parallel to the water surface. Briefly, considering en... | g12242 | [
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<p><strong>Q1:</strong> As we know, in classical mechanics(CM), according to Noether's theorem, there is always one conserved quantity corresponding to one particular symmetry. Now consider a classical system in a $n$ dimensional general coordinates space described by the Lagrangian $L(q,\dot{q})$, where $q=(q_1,...,q_... | g12243 | [
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<p>Suppose there are two wheels linked by some kind of apparatus with a transmission, in a vacuum. Wheel A is spinning, wheel B is not. Is it empirically possible for the transmission to transfer the energy from wheel A to wheel B such that wheel A stops spinning and wheel B spins at a speed very close to that which wh... | g12244 | [
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<p>In boiling soapy water, globs of soap coalesce as the temperature increases to boiling. Does this mean that temperature increases the gravitational pull of bodies?</p> | g12245 | [
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<p>The difference between <a href="http://physics.stackexchange.com/q/1957">a white object and a mirror</a> is mainly scattering versus reflection. If we neglect this difference and define the reflectivity by input energy minus transmitted energy minus absorbed energy, what is the material with the highest reflectivity... | g12246 | [
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<p>I have been more or less struggeling to understand an equation that is apparently used in almost all books covering crystals in any way.
Basically every book that I have found explains the following:</p>
<p>In a system with a one-component vapour at the phase boundary vapour-solid, the difference in chemical potent... | g12247 | [
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<p><img src="http://i.stack.imgur.com/jLunv.gif" alt="enter image description here"></p>
<p>Assuming $T_1$ is the force that acts on box $1$ and $T_2$ is the force that acts on box $2$.</p>
<p>Exactly what causes the Tension? Why does $T_1 = T_2$?</p>
<p>The problem is we are told to memorize that $T_1 = T_2$ for ma... | g12248 | [
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<p>I was reading my Engineering Mechanics book, and it derived some strange looking integrals I'll have to apply. I could memorize them, but I'd rather understand them - then I won't have to memorize. </p>
<p>A few words mentioning Leibniz notion, and viola - we have these relationships:</p>
<p>$$\int_{v_0}^vdv=\int_... | g12249 | [
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<p>Through the photoelectric effect among many others we learn that light is actually comprised of discreet quanta of energy. That's because of the energy of the emitted electrons as well as the minimum frequency of incident light that is able to start the process. A photon of frequency (energy) less than the threshold... | g388 | [
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<blockquote>
<p>The distance to the galaxy NGC3198 is found to be $15.9 MPc$ and recession velocity is $680km s^{-1}$. What value of Hubble Constant is implied? If $H_0$ is in fact $72 km s^{-1} Mpc^{-1}$, what does this imply?</p>
</blockquote>
<p><strong>Attempt</strong></p>
<p>Using $v = H_0D$, I found $H_0 = 49... | g389 | [
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<p>Energy is defined more in the mathematical sense, and tends to show true with observations in the physical world.</p>
<p>But why is energy conserved aside from "<a href="http://en.wikipedia.org/wiki/Noether%27s_theorem" rel="nofollow">Noether's theorem</a>"?</p>
<p>In a closed system that has an energy $E$, we kno... | g12250 | [
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<p>Suppose I have a Gold Leaf Electroscope and the leaves are observed to diverge by a certain amount. Now if I send a beam of X-rays and allow it to fall upon the electroscope for a very short period of time, what exactly will happen?</p> | g12251 | [
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<p>I was reviewing some analytical chemistry and stumbled upon a section that explained the imperfection of using a salt bridge. </p>
<p>It said that the using dissimilar ions is a problem because in, for example, the case of KCl the $K^+$ and $Cl^-$ have different mobility and so you get regions that are rich in $K^+... | g12252 | [
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<p>I understand the concept of why the signal speed is higher than the electron drift velocity, but I can't understand the concept of joule heating. If electrons move slow then how do they produce a lot of heat when they hit the nucleus. Besides my friend once told me that the drift velocity is the net movement and e... | g12253 | [
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<p>How do you explain point 44 of the attached pdf document on surface tension? Here's the <a href="http://www.sakshieducation.com/EAMCET/QR/Physics/Jr%20Phy/12Surface%20tension%20_198-208_.pdf" rel="nofollow">link</a>.</p>
<p>How is the direction of surface tension found out?
(I know it tangential but in which direc... | g12254 | [
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<p>In <a href="http://www.sciencemag.org/content/318/5851/766.abstract" rel="nofollow">"Quantum Spin Hall Insulator State in HgTe Quantum Wells"</a>, researchers observed a 2D topological insulator by sandwiching HgTe between CdTe. Is the CdTe really necessary? Would Vacuum/HgTe/Vacuum itself be a topological insulat... | g12255 | [
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<p>Is it possible to design a physical experiment that shows that a time limited signal, such as a rectangular pulse is composed of infinite continuous sine/cosine waves?</p> | g12256 | [
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<p>I've seen multiple times now in MotoGP that motorcycles were leaving a curve, and because of the acceleration the front wheel is slightly leaving the ground. But at the same time they were still leaning to the inside of the curve, just following the curve to the end and then going straight again.</p>
<p>Now I under... | g12257 | [
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<p>I'm just starting to come across <a href="http://en.wikipedia.org/wiki/Path_integral_formulation" rel="nofollow">path integrals</a> in quantum field theory, and want to get the right intuition for the them from the start. The amplitude for propagation from $x_a$ to $x_b$ is typically written </p>
<p>$$U(x_a,x_b)=\i... | g12258 | [
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<p>I hope that I am using appropriate terminology. My confusion about quantum theory (beyond my obvious unfamiliarity with its terminology) is basically twofold: </p>
<ol>
<li>I lack an adequate understanding of how the <em>mathematics</em> of quantum theory is supposed to correspond to phenomena in the physical world... | g12259 | [
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<p>if I stretch two wires parallel to each over and in a little distance and I let through them slow moving electrons, do I measure a current in the wires? Of course the electrons don't hit the wire. Some sources where such experiments described? </p> | g12260 | [
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<p>In single slit diffraction, why (according to the equation for $\theta$) do successive dark spots exist at whole number intervals ($n=1,2,3, \ldots$) and not half? The correct path difference for destructive interference is $1/2$ a wavelength, so why in $\theta = n(\lambda)/(\mbox{slit width})$ do we use $n = 1,2,3,... | g12261 | [
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<p>Is there a substance that doesn't reflect or absorb visible light but may reflect light from another spectrum? Is there a theoretical substance that would have these properties?</p>
<p><strong>EDIT</strong>:<br>
Sorry I wasn't quite clear with my original question. I've updated it to express more what I was thinkin... | g12262 | [
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<p>Can someone show me a formula in order to convert an angle from [V] to degree or rad? (i use aPotentiometer measuring steering angle)</p>
<p>Edit: Well let me exlpain it. I photo of my experiment is shown below. I apply a force to my material and measure the torsion angle with a potentiometer. For example for P=1,1... | g12263 | [
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<p>I am fascinated by the gyroscope, like everyboy who was so lucky as to get such a toy as a kid. But probably also grown-ups are not immune to its charm.
I am not asking for a theoretical explanation. My question is more practical:</p>
<p><strong>I am looking for a clear and simple way to determine quantitatively t... | g12264 | [
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<p>What is the significance of the <a href="http://www.google.com/search?as_epq=magnetic+translation+operator" rel="nofollow">magnetic translation operator</a> used in describing the <a href="http://en.wikipedia.org/wiki/Fractional_quantum_Hall_effect" rel="nofollow">Fractional Quantum hall effect</a>? I was following ... | g12265 | [
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<p>My General relativity skills suck. I need a good paper that</p>
<ul>
<li>does not start with equivalence principle and pages of elevator experiments</li>
<li>derives principles mathematically, not by physical intuition</li>
<li>explicitly shows how to compute things, again not via Penrose diagrams, in fact<br>
just... | g390 | [
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<p>I may be badly mixing things up here. If I am, please kindly correct me.</p>
<p>As I understand it, if the universe was too dense at the start of the big bang, it would have collapsed back in on itself. Too sparse, and it would have expanded violently leaving no galaxies. I also read that the ratio of the actual de... | g12266 | [
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<p>Does any branch of physics, study the passing off of information/knowledge from one body to another ( body would obviously be living beings here, as they only can do so ). And resultant changes in the physical state of the universe because of that information. </p>
<p>For example, whatever physical state, a living ... | g12267 | [
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<ol>
<li><p>From <a href="http://en.wikipedia.org/wiki/CPU_power_dissipation#cite_note-0" rel="nofollow">Wikipedia</a></p>
<blockquote>
<p>The power consumed by a CPU, is approximately proportional to CPU
frequency, and to the square of the CPU voltage: $$
P = C V^2 f $$ (where C is capacitance, f is freq... | g12268 | [
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<p>How would quantum mechanics explain doppler effect?</p>
<p>And just for curiosity, is there any effect similar to doppler effect occuring at quantum level?</p> | g12269 | [
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<p>Is there an example where model building that is motivated only by Naturalness, has led to experimentally verified observations?</p>
<p>If the question is unclear, or if the reader wants more elaboration, then continue reading.</p>
<p>Naturalness is defined by 't Hooft as: "A theory with a parameter $m$ is natural... | g12270 | [
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<p>i heard that fission activation energy of (235)U is less than of neutron separation energy of (236)U <strong>so this must the reason that (235)U is fission able</strong></p>
<p>$$E_s+(236)U\to (235)U+n$$
in this interaction $E_s$ is neutron separation energy ( energy required to separate neutron )</p>
<p><img src... | g12271 | [
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<p>Basically I need to get an initial vertical velocity to make the ball reach a specific height, but also I need to get a horizontal verlocity so that the ball will travel the distance. For an example lets say the distance is 100m and the max height is 50m starting at 0m. Any help is welcome appreciated.</p>
<p>Also ... | g12272 | [
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<p>I don't have a clear picture of what is "by definition" the multiverse appearing in the models of eternal inflation. A long time ago I heard that it is a quantum state, but in the cosmology books I have looked into (all treating the subject superficially, may I suspect it's because the object is still not clearly de... | g12273 | [
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<p>How can I interpret the parameter <em>temperature</em> $T$, if I'm not given the description of the system in terms of the equation of state, $E(S,V\ )$ or $S(E,V\ )$ and so on.</p>
<p>In many systems it makes sense to think of it as an "energy" itself, e.g. when the entropy is such, that $T$ basically represents t... | g12274 | [
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<p>Imagine that one could theoretically trap a single electron in a small box, with walls that somehow prevent the electron from passing through and out of the box. Now, the box begins to move in on itself, gradually cornering and trapping the electron. The box continues trapping the electron until it perfectly encases... | g12275 | [
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<p>If we consider a charged black hole in AdS spacetime, we can either do thermodynamics in the grand canonical or the canonical ensemble. In the former, we fix the electrostatic potential $\Phi=A_t(r=\infty)$ at the boundary of the bulk such that $\left<Q\right>=-\frac{1}{\beta}\left(\frac{\partial S}{\partial\b... | g12276 | [
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<blockquote>
<p>"..." First, we will familiarize us with a collision between a homogeneous beam of length,
$L$, mass $M$ attached with a frictionless hinge in point $O$ at one of the endpoints of
the beam. The moment of inertia of the beam for rotations around the point $O$ in the
direction given by the hinge i... | g12277 | [
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<p>On studying quantum states of the hydrogen atom, I came with a question: what is the precise definition of a <a href="http://en.wikipedia.org/wiki/Quantum_state" rel="nofollow">quantum state</a>? Particularly, when solving the Schroedinger eq for the H using separation of variables, the quantum numbers and wavefunct... | g12278 | [
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... |
<p>I have tried to understand paragraph 10.7 (Kallen-Lehmann Representation) in Weinberg's Quantum theory of fields (vol.1). He calculated matrix element </p>
<p>$$\langle0|\Phi(0)|p\rangle =(2\pi)^{-3/2}\left(2\sqrt{p^{2}+m^{2}}\right)^{-1/2}N.\tag{formula 10.7.19}$$</p>
<p>$N$ is constant. I can't understand how it... | g12279 | [
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<p>For ordinary spontaneously broken symmetries, you can demonstrate relations between S-matrix elements with a soft <a href="http://en.wikipedia.org/wiki/Goldstone_boson" rel="nofollow">goldstone</a> emission and another S-matrix element without the emission. </p>
<p>If I break SUSY I get <a href="http://en.wikipedia... | g12280 | [
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<p>I came upon this while studying S.H.M.</p>
<p>Well,is there a difference between writing</p>
<p>$$a=\frac{dv}{dt}\;$$</p>
<p>and $$a=v\frac{dv}{dx}\;$$
do they differ on the basis of one being a vector and the other being a scalar equation?Please explain.</p> | g12281 | [
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<p>are sub-atomic particles really particles or mere concepts in our minds? do they exist independently of human thought?</p>
<blockquote>
<p>In the tenth century, Ibn al-Haytham initiated the view that light
proceeds from a source, enters the eye, and is perceived. This picture
is incorrect but is still what mo... | g12282 | [
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<p>So I'm hoping I can get some help. I have a 2d image and need to get the 1d power spectrum. I know the basic steps: take fft, take fft^2 to get power, then take average power in radial bins to get 1d power- but it's in the details that I'm unsure.</p>
<p>The image has been smoothed/convolved with a Gaussian beam. I... | g12283 | [
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0.08755... |
<p>What is your opinion of the hawking radiation mechanism, does that actually lower the entropy of the black hole?</p> | g12284 | [
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<p>I have derived the <a href="http://en.wikipedia.org/wiki/Larmor_formula" rel="nofollow">Larmor equation</a> as $$P = \frac{q^2}{6\pi \epsilon_0 c^3} |\ddot{r}|^2.$$ </p>
<p>How do I make this relativistic?
Apparently, I have to consider the acceleration parallel and perpendicular to the velocity of the accelerating... | g12285 | [
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<p>Imagine we have a frictionless semicircular skateboard ramp and we release a cart filled with sand from one edge of the ramp. The cart has a hole and it loses sand at a constant rate. My question is will the cart reach the other extreme edge of the ramp or will it stop midway and slide back down?</p>
<p>I am confus... | g12286 | [
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<p>We have several definitions of distances in cosmology. Take angular diameter distance. $$d_A = a(t)\int \frac{dt}{a(t)}\;.$$ If an object has proper length $L$ then the angle $\theta$ it is seen at is</p>
<p>$$\theta = \frac{L}{d_A}$$
This is similar to the way an angle $\theta$ and arc length $s$ are related in a... | g12287 | [
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<p>My question: Is it possible to manufacture a lens whose focal point doesn't shift in any direction during the day when the sun shines from different angles? It is understood that the focused energy will reach a maximum only if the lens is in the ideal angle to the sun, but I need to build a system that always collec... | g12288 | [
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<p><a href="http://en.wikipedia.org/wiki/Gamma_matrices" rel="nofollow">This Wikipedia page</a> explains that for each of the four main gamma matrices $\gamma^{\mu}$, you can find the covariant matrices $\gamma_{\mu}$ with the equation $\gamma_{\mu} = \eta_{\mu\nu}\gamma^{\mu}$. But that formula doesn't make any sense ... | g12289 | [
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<p>How does one use the concept of microstate evolution and definition of macrostate in a consistent manner. As my understanding goes the thermodynamic concepts are defined in equilibrium. How does one apply these concepts in situations out of equilibrium.</p>
<p>I am looking for a simple example involving thermodynam... | g12290 | [
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<p>Special relativity says that anything moving (almost) at the speed of light will look like its internal clock has (almost) stopped from the perspective of a stationary observer. How do we see light as alternating electric and magnetic fields? Also does light never age? </p> | g361 | [
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<p>I know that thought experiment about trains when a flash of light in the middle reaches the both end simultaneously for a passenger but different times for the bystander.</p>
<p>So were there (non-thought) experiments that directly checked this?</p> | g12291 | [
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0.... |
<p>I see the similarity between the Lattice Gauge and Spin Network .
(For example , the both theories depict the node part as quantum (the latter is explained as spin))
Are there any other mathematical,Physical similarity between the two theories ?</p> | g12292 | [
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... |
<p>When reading some literatures on topological insulators, I've seen authors taking Brillouin zone(BZ) to be a sphere sometimes, especially when it comes to strong topological insulators. Also I've seen the usage of spherical BZ in these answers(<a href="http://physics.stackexchange.com/questions/104258/topological-in... | g12293 | [
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<p>If we obtain something like a single isolated hydrogen atom I.e. $H^+$ is it possible by keeping it in a system of charged rings to contain and stop it at the centre of the system?</p>
<p>Any positively charged ring would have electric field pointing towards its centre, if the ion tries to move then it will be push... | g12294 | [
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<p>I have a length of string and I want to know the maximum tension the string can support. I tie one end of the string to the ceiling and the other end to a glass of mass 100 g. The glass is cylindrical, with a cross-sectional radius of 4 cm and a height of 15 cm. I fill the glass with water (density of 1 g/cm3) and d... | g12295 | [
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... |
<p>Grocery stores often have spring scales in their produce department to weigh fruits and vegetables. </p>
<p>The pan of one particular scale has a mass of 0.5 kg, and when you place a 0.5 kg sack of potatoes on the scale the pan lowers by 6 cm. </p>
<p>As we reach for the potatoes to toss in the cart, we accidental... | g12296 | [
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0.0581383... |
<p>This is in continuation to my <a href="http://physics.stackexchange.com/questions/8303/does-the-hup-alone-ensure-the-randomness-in-qt">previous question</a>. It is not a duplicate of the previous one. This question arises because of the answers and discussions in that question.</p>
<p>Can we call a theory, quantum ... | g12297 | [
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0... |
<p>Researchers at Michigan State University recently invented the <a href="http://www.physorg.com/news/2011-03-msu-prototype-video.html/" rel="nofollow">Wave Disk Generator</a> that is supposed to get 60% fuel efficiency. What allows it to be so much more efficient than a traditional Internal Combustion Engine?</p>
<p... | g12298 | [
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<p>If we look at the atomic positions in a single crystal sample with a diamond like lattice, there exist directions along which there are long hexagonal "tubes" (I'm not sure if these have a proper term). </p>
<p><img src="http://i.stack.imgur.com/a4Y2v.jpg" alt="hexagonal tubes in diamond like lattice"></p>
<p>Thi... | g12299 | [
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<p>What is a <a href="http://en.wikipedia.org/wiki/Virtual_ground" rel="nofollow">virtual ground</a>? I would like to know what it is.</p> | g12300 | [
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<p>The field equations (e.g. Schrödinger’s/Maxwell’s) describe the four-dimensional universe as the time evolution of a three-dimensional system. This implies that the universe contains only three dimensions of information: the fourth is derivable deterministically (albeit not practically) from the other three via the... | g12301 | [
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<p>One of the active research areas in present is Strong interacting, Strong Coupling, Strong Correlated regime of the phases of matters.</p>
<p>It seems to me that some physicists in the fields often mix the usages of these twos: <strong>Strong Coupling, Strong Correlated</strong>.</p>
<p>However, in my viewpoint, t... | g12302 | [
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<p>Suppose a large mass $M$ travelling at $v$ impacts a small stationary mass $m$, then following through the elastic collisions from high school, we get that the smaller mass can exit the collision FASTER than $v$.</p>
<p>In the limit of huge $M$, we can change reference frame and make $M$ basically stationary, and $... | g12303 | [
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<p>I want to understand clearly why $ P \gamma^{\mu} P = \gamma^{\mu} $, where $ P $ is the parity operator. </p>
<p>This result follow for example from pag. 66 of Peskin-Schroeder.
The parity operator acts on Dirac fields in this way: $ P \psi (t, \textbf{x}) P = \gamma^0 \psi (t, -\textbf{x}) $, assuming no other p... | g12304 | [
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<p>I started a little bit of Googling around the topic, and found very few information. There are mainly upper limits. I found lower limits only to the rest mass differences of the different neutrino flavors.</p>
<p>Thus, what are the actually current known lower mass limits to the <a href="http://en.wikipedia.org/wik... | g12305 | [
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<p>For determining the drift velocity of a flow of charge we need to find the <strong>average relaxation time</strong> for that flow at that specific temperature.</p>
<p>My question is, how does one find that? Is there some experimental way to find that? Or it is derived by some Mathematical derivations and statistica... | g12306 | [
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