question stringlengths 37 38.8k | group_id stringlengths 2 6 | sentence_embeddings listlengths 768 768 |
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<p>I'm a physics tutor. I'm stuck up with this question. I've no clue about how to proceed with this question. Can any one help?</p>
<blockquote>
<p>A 2 Kg block moving with 10 m/s strikes a spring of constant π^2 N/m attached to 2 Kg block at rest kept on a smooth floor. The time for which rear moving block remain ... | g16295 | [
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<p>So here's the problem background: A projectile of mass m is shot straight up with initial velocity vo and feels a quadratic
air resistance force of the form $F = −kv^2$, where $k ≡ mg/u^2$. ($k$ and $u$ are constants and $g$ is the acceleration of gravity.)</p>
<p>In the first part I was asked to find the speed of ... | g16296 | [
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<p>Why are umbrellas specifically in black? Of course we do have colored ones, but black is the majority. Is there any scientific reason behind it?</p> | g16297 | [
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<p>I'm a physics tutor. This is the question from a High school book.</p>
<blockquote>
<p>The equation of an equipotential line in an electric field is y = 2x,
then the electric field strength vector at (1, 2) may be </p>
<p>a. 4i+3j b. 4i+8j c. 8i+4j d. -8i+4j</p>
</blockquote>
<p>Becau... | g16298 | [
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<p>I'm a physics tutor. This is not a homework problem. I'm unable to solve this problem.</p>
<p>The energy of electric interaction between these dipoles will be:</p>
<p><img src="http://i.stack.imgur.com/Qfaqn.png" alt="enter image description here"></p>
<p>Choose the correct answer from:</p>
<p><img src="http://i... | g16299 | [
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<p>Basically, the book is Brian Cox's <em>Why Does $E=mc^2$?: (And Why Should We Care?)</em>.</p>
<p>I just finished Chapter 5, where we derived the spacetime momentum vector (energy-momentum four vector, as he establishes the physics jargon).</p>
<p>Let $\gamma=\frac{1}{\sqrt{1-\frac{v^2}{c^2}}}$</p>
<p>So, as we f... | g16300 | [
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<p>The particle in an infinite potential well in QM is usually solved by easily solving Schrodinger differential equation. On the other hand particle in the harmonic oscillator oscillator potential can be solved elegantly algebraically using the creation and annihilation operators to find its spectrum.</p>
<p>Is it po... | g16301 | [
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<p>Are the mass dimension of the Dirac field different from those of the Klein-Gordon field, or is this just another issue of "cannonical normalization?"</p>
<p>For instance if $\mathcal{L}_{KG}=\int d^4x\partial^\mu\psi^*\partial_\mu\psi+m^2\psi^*\psi$ the dimension of the field is clearly (to me) $d=1$. With Dirac ... | g16302 | [
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<p>For astronomy, as originally invented, the <a href="http://www.google.com/search?as_q=hanbury+brown+twiss+interferometer" rel="nofollow">Hanbury Brown Twiss interferometer</a> is good for finding the angular diameter of stars and is not a rapidly fluctuating observable like the amplitude in ordinary interferometry. ... | g16303 | [
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<p>Here's a simple 'derivation' of the Brownian motion law that after N steps of unit distance 1, the total distance from the origin will be sqrt(N) on average. It's certainly not rigorous, but I'm wondering if people think it's reasonable, or possibly even a commonly known.</p>
<ol>
<li><p>An object takes one step fr... | g16304 | [
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<p>What is <a href="http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation" rel="nofollow">Schrödinger's wave equation</a>?</p>
<p>We recently studied about the Schrödinger wave equation in school. I understand that because of Heisenberg's Uncertainty principle, and De Broglie's Hypothesis, it was not possible to cons... | g16305 | [
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<p>as per to einstein as we go far from the earth the TIME tends to slow down , so it means when I am one metre above the earth's surface , the time has slow down for me as per <a href="http://en.wikipedia.org/wiki/Gravitational_time_dilation" rel="nofollow">http://en.wikipedia.org/wiki/Gravitational_time_dilation</a> ... | g291 | [
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<blockquote>
<p><strong>Possible Duplicate:</strong><br>
<a href="http://physics.stackexchange.com/questions/28519/two-particles-are-interacting-through-gravitational-forces-how-to-find-their-po">Two particles are interacting through gravitational forces. How to find their positions in function of time?</a> </p>
<... | g497 | [
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<p>I am stuck with one formula in the CFT book by Di Francesco and al. Chapter 3. Equation 3.46 third step, for those who don't have the book, he integrates out degrees of freedom from the Ising Model by summing over some blocks and defining new variables </p>
<p>$$\Sigma_I ~:=~ \frac{1}{R}\sum\limits_{i \in I} \sigma... | g16306 | [
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<p>A black hole power plant (BHPP) is something I'll define here as a machine that uses a black hole to convert mass into energy for useful work. As such, it constitutes the 3rd kind of matter-energy power (formerly "nuclear power") humans have entertained, the first two being fission and fusion. Putting aside the fa... | g16307 | [
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<p>The wavelength of a particle of momentum p is calculated using De Broglie relation.
The de Broglie relation was postulated for what is called a matter waves. Now according to the statistical interpretation of QM we know that there is no matter waves. It is an abstract wave called the wave function which describes th... | g16308 | [
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<p>There is a picture usually depicted in introductory quantum mechanics about how the probability pattern appears in the classical limit, that the oscillation is too fast and that it cannot be resolved by the experimental apparatus, hence the detector will detect only the average value.</p>
<p><img src="http://i.stac... | g16309 | [
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<blockquote>
<p><em>(Q) Find the maximum speed at which a truck can safely travel without toppling over, on a curve of radius 250m. The height of the centre of gravity of the truck above the ground is 1.5m and the distance between the wheels is 1.5m, the truck being horizontal.</em></p>
</blockquote>
<p>I actually c... | g16310 | [
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<ol>
<li>How does an electro-magnetic waves get detached from an antenna and spread to the space?</li>
<li>While an antenna receives an EM wave, which quantity of the EM wave (electric or magnetic) is used for converting the EM wave to electric energy. i.e, fluctuating magnetic field or fluctuating electric field produ... | g16311 | [
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<p>From an aerodynamic point of view, could a full-size aircraft of X-Wing design fly in Earth's atmosphere? Assuming you were free to add control surfaces here and there, could the wings in open configuration create lift ? </p>
<p><img src="http://i.stack.imgur.com/GS4Mt.jpg" alt="X-Wing"></p> | g16312 | [
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<p>I have a few questions related to the following interaction Lagrangian (no use of crossing symmetry in the following) involving the uncharged scalar $\chi$ and the charged scalar $\phi$: </p>
<p>$$\tag{1}\mathcal{L}_{\rm int} ~=~ \sqrt\lambda· g· \chi\phi^\dagger \phi - \frac{\lambda}{4}(\phi^\dagger\phi)^2.$$ </p>... | g16313 | [
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<p>What is the color of Water? I am not talking about large water bodies like Ocean or lake but a glass of water. If it has no color how can we see it?</p> | g16314 | [
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<p>There is an idea that the geometry of physical space is not observable(i.e. it can't be fixed by mere observation). It was introduced by H. Poincare. In brief it says that we can formulate our physical theories with the assumption of a flat or curved space by changing some assumptions and these two formulations are ... | g16315 | [
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<p><a href="http://www.youtube.com/watch?v=bm6ScvNygUU" rel="nofollow">Here</a> is a video of Michio Kaku discussing Moore's Law and the quantum mechanical limits thereof. </p>
<p>Around the 1:30 mark he's talking about how the chips today have a layer of 20 atoms across (I'm assuming Silicon atoms?). He goes on to s... | g16316 | [
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<p>Heat can be evolved or absorbed when two dissimilar liquids are mixed together at constant temperature and pressure. This is called the heat of mixing of the mixture.</p>
<p>I'm trying to understand the molecular "picture" associated with this process. Here is my current attempt:</p>
<p>Initially, there are two ... | g16317 | [
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<p>A lot has been said as to why quantum mechanics needs complex numbers.</p>
<p>However, all measurements produce real values. Expectation values are real, the observables form a real Lie-algebra (use $-\mathrm i[·,·]$ as Lie bracket instead of the raw commutator) and any state $\mathbf z$ is uniquely deter... | g16318 | [
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<p>Most GPS receivers and smart phones contain an "electronic compass", which I understand is generally a Hall effect magnetometer. These devices generally require "calibration", which involves waving the device in an <a href="http://www.s3sensor.com/en/s3/calibration/">8-shaped figure</a>. During the motion, the forwa... | g16319 | [
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<p>Why is Silver-108 unstable if silver-107 and silver-109 are stable?
I found it on crash course but no answer was given. </p> | g16320 | [
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<p>A beam of light of width $W$ and wavelength $\lambda$ with divergence that is diffraction-limited is refocused with an optical element placed at a distance $D$ from the beam source. Will the refocused beam have worse divergence than the one imposed by diffraction limits? how much worse? </p>
<p>Is there an optical ... | g16321 | [
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<p>What is the difference between <a href="http://en.wikipedia.org/wiki/Impulse_%28physics%29" rel="nofollow">impulse</a> and <a href="http://en.wikipedia.org/wiki/Momentum" rel="nofollow">momentum</a>?</p>
<p>The question says it all...I know the second of of them is mass * velocity, but what is the first one for, an... | g16322 | [
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<p>I just read the wikipedia page</p>
<p><a href="http://en.wikipedia.org/wiki/Gravitational_potential" rel="nofollow">http://en.wikipedia.org/wiki/Gravitational_potential</a></p>
<p>But I don't understand how to get this formula:</p>
<p>$$\rho(\mathbf{x}) = \frac{1}{4\pi G}\Delta V(\mathbf{x})$$</p>
<p>Can anyone ... | g16323 | [
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-0.12296302616596222,
-0.05068603903055191,
-0.02606281451880932,
0.04129548370838165,
0.039777833968400955,
0.00506... |
<p>Venus rotates approximately 6.5 km an hour Earth rotates approximately 1650 km/h how fast could we speed up Venus's rotation via only weather manipulation ( maybe a giant fractal lens between Venus and the Sun at a gravitationally equilibrium point, the lens redirecting all the energy hitting Venus shifting it so... | g16324 | [
0.0054665724746882915,
0.05151508376002312,
0.009292062371969223,
0.025521034374833107,
0.047870270907878876,
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0.07719305902719498,
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0.03694188594818115,
0.011642699129879475,
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-0.... |
<p>A particle of mass m moves on the x-axis under the influence of the potential
$$V(x)=\frac{1}{2}m\omega^2x^2+Fx$$
Can anyone help me, using Schrödinger's equation in one dimension that the energy levels are:
$$E_n=(n+\frac{1}{2})h\omega-\frac{1}{2}\frac{F^2}{m\omega^2}$$
Where n is a non negative integer?</p> | g16325 | [
-0.045868437737226486,
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0.03100067749619484,
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... |
<p>Three resistances AB, BC, CD are joined in series and placed across the terminals of a galvanometer. The resistance of the galvanometer is 15 ohm and it gives full scale deflection for a current of 5 milliampere. Find the value of each of the resistances so that the instrument will serve as a multi-range ammeter, us... | g16326 | [
0.010037833824753761,
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0.02742786519229412,
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... |
<p>Maybe another stupid question, but what's the energy of a graviton?
Is it $\hbar \omega$?</p>
<p>Does it emit gravitons when an apple falls onto the ground, like photons be emitted when an electron transits from a higher energy level to a lower one?</p> | g16327 | [
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<p>I have checked some Quantum Field Theory texts that include basic QED and they all include the Feynman rule that each vertex bring with it a factor of $$\pm i e \gamma^\mu$$ but I have yet to find a derivation of this rule. How can we start from the interaction term in the Lagrangian, $-e \bar{\psi}\gamma^\mu A_\mu ... | g16328 | [
0.04231778904795647,
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0.01219096314162016,
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<p>In quantum mechanics, a particle may tunnel through a barrier it would not be able to surmount in a classical sense.</p>
<p>My question is this:</p>
<p><strong>What are all the factors that may prevent a photon from propagating (thus it would need quantum tunneling to do so), and can they be described in a general... | g16329 | [
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0.01... |
<p><a href="http://en.wikipedia.org/wiki/Holographic_principle" rel="nofollow">Holographic principle</a> or Maldacena's duality is a theory that says that the volume of space can be described by just looking the information encoded on a boundary to the region of that space.</p>
<p><a href="http://en.wikipedia.org/wiki... | g16330 | [
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<p>According to Kolmogorov, the energy spectrum function of a turbulent fluid is given as,</p>
<p>$E(k)=C\epsilon^{\frac{2}{3}}k^{\frac{-5}{3}}$</p>
<p>where $\epsilon$ is the energy flux and $k=\frac{2\pi}{r}$ where $r$ is the length scale. </p>
<p>The normal explanation I see in most physics texts and articles is ... | g16331 | [
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<p>I was always wondering where the feeling of fuzz comes from when touching a CRT (Cathode Ray Tube) television on its display screen when the TV is turned on. Can someone please explain why I feel something fuzzy whenever I touch a CRT television screen when it is on?</p>
<p>It would be most appreciated if it can be... | g16332 | [
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0.1010... |
<p>I have some questions about Pade approximants.</p>
<ol>
<li><p>Given a divergent power series $ \sum_{n >0} a(n)x^{n} $ can we use a Pade Approximant to it $ R(x)$ so we can obtain a SUM of the series for every $x$ ?</p></li>
<li><p>Given a Taylor power series $ \sum_{n >0} c(n)x^{n}=O(x^{a}) $ for positive $... | g16333 | [
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<p>In section 2.3.4 of Di Francesco, Mathieu, Senechal's <em>Conformal Field Theory</em> (and I would guess in many other introductory discussions of QFT) one finds a simple sample computation of a propagator</p>
<p>$$K(x,y) := \langle \varphi(x)\varphi(y)\rangle.$$</p>
<p>In the example, the fields $\varphi:\mathbf{... | g16334 | [
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<p>Imagine two blocks of masses $m_1$ and $m_2$ joined together by a spring of spring constant $K$.</p>
<p>Now let the spring be stretched by a distance $X$ and then the system is released. suppose during the stretching the block of mass $m_1$ moves towards left by a distance $A$ and the block of mass $m_2$ by a dista... | g16335 | [
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<p>Suppose we have Euler-Lagrange system with generalized coordinate $r_1$ and $r_2$, and input $u_1$ and $u_2$. I know how to prove this system is indeed Euler-Lagrange system.</p>
<p>Suppose now if we have a constraint equation so $r_1=f_1(q)$ and $r_2=f_2(q)$. How would I approach in proving that this constrained s... | g16336 | [
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<p>In Landau and Lifshitz's Stat Mech Volume I is the comment:</p>
<blockquote>
<p>However, despite this symmetry, quantum mechanics does in fact involve an
important non-equivalence of the two directions of time. This appears in connection with the interaction of a quantum object with a system which with
suff... | g16337 | [
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<p><img src="http://i.stack.imgur.com/daiFb.png" alt="enter image description here"></p>
<p><strong>I have problem in understanding equation (1.23), I croped this image from Mark_Srednicki "Quantum field theory". Can anyone show me the reason for the equation (1.23)?</strong></p> | g16338 | [
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<p>Some expensive electronics or mechanical devices are designed to be shock-resistant. However, the manufacturers often market the level of shock-resistance in units of g-force (I know g-force is really a measure of acceleration). I'm not really convinced that that's the proper unit.</p>
<p>In fact, the Wikipedia art... | g16339 | [
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<p>In one section of his auto-biography, <em><a href="http://rads.stackoverflow.com/amzn/click/0465001165" rel="nofollow">Alvarez: Adventures of a Physicist</a></em>, <a href="http://en.wikipedia.org/wiki/Luis_Walter_Alvarez" rel="nofollow">Luis Alvarez</a> describes a tour of Antarctica. This comment about a flight o... | g16340 | [
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<p>Today a friend's 6 year old sister asked me the question "why don't people on the other side of the earth fall off?". I tried to explain that the Earth is a huge sphere and there's a special force called "gravity" that tries to attract everything to the center of the Earth, but she doesn't seem to understand it. I a... | g16341 | [
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<p>I am wondering if a wave packet of a single photon in the time domaine
$$
\psi(t)=|\psi(t)|\; \text e^{\text i \varphi(t)}
$$
can have a different $t$ dependence in phase than the simple phase $\varphi(t)=\omega_0 t$ ?</p>
<p>The big theoretical advantage of such a simple phase is that the fourier transormation of ... | g16342 | [
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0.0030264316592365503,
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... |
<p>Why is it that when you first fill up a balloon, it's hard to get air through, but after inflating it a bit, it becomes much easier to further inflate the balloon?</p> | g16343 | [
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<p>I am trying to gain a better understanding of thermodynamic equilibrium. Here's what (I think) I know:</p>
<p>If a system is in Thermal, Radiative, Chemical, and Mechanical Equilibrium, then it is in thermodynamic equilibrium.
When in this state, the system can do no work as there is no available free energy to use... | g16344 | [
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0.005236178636550903,
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<p>Assumptions:</p>
<ol>
<li>Cross terms in strain tensor are defined as equal $\varepsilon_{xy} = \varepsilon_{yx}$.</li>
<li>pure mode I crack.</li>
<li>Far from crack tip, material is purely elastic and we are way below
yield stress => $\varepsilon_{ij} \propto \sigma_{ij}$.</li>
<li>Cross term $\sigma_{yx} $in lin... | g16345 | [
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0.018896324560046196,
... |
<p>I'm preparing my statistical physics course, and while writing the lecture notes it says that a system with non distinguishable particles has much less microstates asociated with a particular macrostate. Hence, a system with distinguishable particles has much more microstates asociated with a particular microstate. ... | g16346 | [
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0.062309108674526215,
-0.0... |
<p>As the title says, I have no idea what these things are or how to get or use one. Can I receive a simple explanation or links to one? I'm a computer engineer so I have very little physics/mechanical engineering background.</p> | g16347 | [
0.02491338737308979,
0.02167094312608242,
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<p>in 3D, electric field of a piont charge is inversely proportional to the square of distance while the potential is inversely proportional to distance. We can derive it from Coulomb's law.
however, I don't known how to derive the formula in 2D and 1D. I read in a book that electric potential of a point charge in 2D i... | g16348 | [
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... |
<p>Let me start off by saying that I never got a degree in any field but I do read and study physics (both classical and quantum); although I personally can't solve quantum physics equations I do have a good understand of the subjects so I don't require a very simple explanation and some math is fine. </p>
<p>With th... | g16349 | [
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<p>Is the following explanation plausible? Can you spot any flaws?</p>
<p>Mars doesn't have a large moon to stabilise its axis of rotation. At some point early in its formation its axis might have been pointing at the Sun with one hemisphere continually heating up and evaporating all the volatiles which circulated to ... | g16350 | [
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0.0219... |
<p>I have been thinking about ways of teaching electronics and I'm wondering if the following is true...</p>
<p>For starters, when we talk about voltage as energy per unit charge, is this energy manifest simply as the kinetic energy of the electron?</p>
<p>So, all other things being equal, will the electrons coming o... | g16351 | [
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0.024106210097670555,
0.034423381090164185,
0.012260561808943748,
0.014853937551379204,
0.0196... |
<p>It has always been a hard time understanding the phenomenon of <a href="http://en.wikipedia.org/wiki/Diffraction" rel="nofollow">diffraction</a> of light around opaque objects. Hoe does it happen? Why does transparent objects do not diffract light? What quantum mechanics operate that bends light? I used to have an i... | g16352 | [
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0.017166297882795334,
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0.049261998385190964,
-0... |
<p>When I first learned about the four fundamental forces of nature, I assumed that they were just the only four kind of interactions there were. But after learning a little field theory, there are many other kinds of couplings, even in the standard model. So why isn't the Yukawa Higgs coupling considered a fifth funda... | g829 | [
0.06073834374547005,
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0.01608756184577942,
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0.0306... |
<p>I noticed a colleague had a tall narrow cup for his coffee, and it got me thinking about whether it would retain heat for longer or not. </p>
<p>Assume two cups, both are cylindrical, and both hold the same volume. One is taller and more narrow, and the other has even width and height dimensions. </p>
<p>My first ... | g16353 | [
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0.04008796811103821,
0.013784196227788925,
0.038377344608306885,
-0.010735945776104927,
-0.006718331947922707,
0.026341712102293968,
-0.08254964649677277,
-0.04802635684609413,
-0.011114506982266903,
0.020693035796284676,
0.024743853136897087,
0... |
<p>Some years ago i read about this equation that helps us estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.</p>
<p><img src="http://i.stack.imgur.com/yqMHa.png" alt="enter image description here"></p>
<p>Now, i am wondering if there are results from <a href="http://... | g16354 | [
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0.01496589370071888,
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0.015358766540884972,
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0... |
<p>Are there all the common optical devices like beam splitters, mirrors, polarizers, fibers, etc for photons with a wavelenght in the range of micro meters?</p>
<p>If so, how broad can the bandwidth be for the optical devices to work properly?</p>
<p>Consider for example a photon with a mean frequency of $10^{12}\,\... | g16355 | [
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<p>As we know that particles, only having charge, can have magnetic moment, then how particle like neutrino (having mass) can have magnetic moment? Don't bother about neutron because it has charge distribution.</p> | g16356 | [
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<p>This page:</p>
<p><a href="https://blog.afach.de/?p=62" rel="nofollow">https://blog.afach.de/?p=62</a></p>
<p>Discusses the error Neil deGrasse Tyson made when talking about electronic transitions (video included there). Tyson clearly said in his Cosmos series that electrons disappear from one level and appear in ... | g16357 | [
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0.02253102883696556,
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0.051613... |
<p>If the universe is expanding why doesn't the matter in it expand proportionally making it seem as if the universe is static? Alternatively, as spacetime expands why does it not just slide past matter leaving matter unmoved? What anchors the matter to a particular point in spacetime? </p> | g56 | [
0.05559362471103668,
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0.049971... |
<p>Given the potential field in free space: </p>
<p>$V = \frac{100xz}{x^2 + 4} $</p>
<p>Assume that the z = 0 surface is a conductor and find the total charge on that portion of the conductor defined by $0 < x < 2, −3 < y < 0$.</p>
<hr>
<p>I have been given an answer but I think it's wrong.</p>
<p>He... | g16358 | [
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0.0086284... |
<p>I'm interested in the (very) low energy limit of quantum electrodynamics. I've seen that taking this limit does not yield Maxwell equations, but a quantum corrected non-linear version of them. </p>
<ol>
<li>If quantum phenomena are responsible for what we see in the macroscipic world, it is expected that there is a... | g16359 | [
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<p>If you </p>
<ol>
<li>take a container of great strength,</li>
<li>fill it to the brim with liquid nitrogen,</li>
<li>seal the container, and</li>
<li>heat it to room temperature.</li>
</ol>
<p>What will the pressure be inside?</p>
<p>Bonus: The same with liquid Helium.</p>
<p>(I posted this
<a href="http://physi... | g498 | [
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0.03898324444890022,
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<p>Why do polarized sunglasses remove (most) reflections on car windows? I know that both lenses of polarized sunglasses are polarized in the same direction and I can see that reflections in my own windshield and the windows of other cars appear, disappear, or change depending on how I tilt my head, but why? Why is t... | g16360 | [
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0.017730051651597023,
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<p>In the elasticity theory, you can derive a wave equation from the fundamental equation of motion for an elastic linear homogeneous isotropic medium:</p>
<p>$\rho \partial^2_t \overline{u} = \mu \nabla^2 \overline{u} + (\mu+\lambda) \nabla(\nabla \cdot \overline{u})$
</p>
<p>But in the seismology tradition, you int... | g16361 | [
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<p>I recently read that the <a href="http://www.livescience.com/environment/050825_earthcore.html" rel="nofollow">earth's core rotates faster than the surface.</a><br>
Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion.</p>
<p>But, what makes a plane... | g16362 | [
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0.00... |
<p>I'm trying to calculate the inertia tensor of a spherical cap (a piece of a sphere) like the one shown below.</p>
<p><img src="http://mathworld.wolfram.com/images/eps-gif/SphericalCap_1001.gif" alt="spherical_cap"></p>
<p>The origin (not shown) is located at the center of the whole sphere and the axes oriented as ... | g16363 | [
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0.08431773632764816,
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-... |
<p>Experiments are showing that larger and larger objects can be entangled whereby proving that this quantum feature has no upper limit. Assuming this is true, does entangled celestial bodies mean even the 2-Body and not just N-body problems are also unsolvable?</p> | g16364 | [
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<blockquote>
<p>The total mass of the children and the toboggan is 66 kg. The force the parent exerts is 58 N (18 degrees above the horizontal). What 3 forces/ components do no work on the toboggan?</p>
</blockquote>
<p>I said the vertical component of the force being applied, since the displacement and the force wi... | g16365 | [
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<p>A ping pong ball is rolling over a smooth (but not frictionless) table. During its travel, a clockwise spin is placed on the ball. The ball's path is changed to move to the right (in perspective from it's initial path). If the friction of the table is a variable $f$ that can be altered, how does one calculate the al... | g16366 | [
0.02060193009674549,
0.014505828730762005,
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0.018725622445344925,
... |
<p>1.How does a Telescope work?
2.What factors increase the magnification of the lens?</p> | g16367 | [
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... |
<p>My first question was answered here: <a href="http://physics.stackexchange.com/questions/119337/deceleration-rate-of-objects-of-different-mass-but-the-same-otherwise">Deceleration rate of objects of different mass but the same otherwise</a> . But based on that, here is a follow-up question (I also edited my first po... | g16368 | [
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<p>For any matrix $U \in SU(2)$ there is an associated map from $S^2$ (the surface of a 3-disk) to itself defined by $\pi \circ U$, where $\pi$ is the projection map from $\mathbb{C}^2$ to $CP(1)$, that is the map associating to a pure state of a qubit its representative on the Bloch sphere.</p>
<p>Is the map $\pi \ci... | g16369 | [
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-0.... |
<p>In regards to the 'conservation of angular momentum' being the explanation of why celestial objects spin...</p>
<p>If you fill a ball or any other container with a liquid and try to spin it, you will not see any more than 5 or 6 revolutions because of the frictional losses of the liquid inside the container.</p>
<... | g16370 | [
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<p>I have a trouble understanding an argument which I think has a simple answer but I am not getting it.</p>
<p>The question is that if you don't impose local fermionic symmetry the GS action has only one term and one of the equation of motion looks as $Γ\cdot p\partial_0\psi=0$, where $\psi$ is a Majorana-Weyl spinor... | g16371 | [
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<p>How are the <a href="http://en.wikipedia.org/wiki/Fundamental_interaction" rel="nofollow">fundamental forces</a> transmitted? In particular I wonder, are all "processes" local, i.e. without superluminal distant interactions? But if they are local, then particles would have to occupy exactly identical space positions... | g16372 | [
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0.030605077743530273,
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<p>So I though, and was told, that entropy is the amount of disorder in a system. Specifically the example of heat flow and it flows to maximize entropy. To me this seemed odd. This seemed more ordered to me, from two things (hot and cold) to one thing (lukewarm). </p>
<p>So as I have read today on wikipedia </p>
<p>... | g16373 | [
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0.03631195053458214,
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0.053527798503637314,
-... |
<p>Does anyone know of link to the derivation of the <a href="http://en.wikipedia.org/wiki/Universal_variable_formulation" rel="nofollow">Universal Variables</a>?</p>
<p>This is in regards to <a href="http://en.wikipedia.org/wiki/Kepler%27s_equation" rel="nofollow">Kepler's equations</a>. The Wikipedia link didn't hav... | g16374 | [
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<p>I came across this picture/sketch on the <a href="http://en.wikipedia.org/wiki/Spacetime">internet</a>, however there is no any explanation about it:</p>
<p><img src="http://i.stack.imgur.com/9ytEW.jpg" alt="enter image description here"></p>
<p>What is "UNPREDICTIBLE"? "UNSTABLE"? "TOO SIMPLE"? "elliptic", "ultra... | g16375 | [
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0.0... |
<p>When I was in high school, my teacher did an experiment to show the power of atmospheric pressure.</p>
<p><strong>Experiment:</strong>
Prepare a glass bottle, fill with water, put a glass plate on the bottle, make sure there is no air in the bottle, just water. Hold the glass bottle and plate, and invert them. Slow... | g646 | [
0.054416097700595856,
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<p>In chapter 80, <em>The Primary</em>, Neal Stephenson has one of his character describe how the drives of a computer carried through a door (by the police, who where raiding the facility) will have been erased.<br>
Basically, there's an enormous electromagnet around the door frame:</p>
<blockquote>
<p>Cantrell is ... | g16376 | [
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<p>This is a difficult question to phrase succinctly, so I hope the title makes sense. What I want to understand is what seems like a lack of symmetry (besides SUSY-breaking) between the SM sector and their superparters.</p>
<p>In SUSY we add a second higgs doublet, so we end up with 8 degrees of freedom. Three are ea... | g16377 | [
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0.02367... |
<p>As the space is a vacuum and there is no friction in space,
Can we assume that, if we place an object in gravity in exactly the right distance from a planet with gravity and in the right acceleration, it will orbit indefinitely, or until another object with a gravitational force will interfere?</p> | g16378 | [
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<p>What's wrong in taking the cat as an observer in Schrodinger's experiment? Plz kindly elaborate! And if possible also describe about possible logics if the question bears the answer <em>No.</em></p> | g840 | [
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<p>I'm looking at a question which starts off as:</p>
<p>A proton is travelling through a material and scattering the electrons in the material. Express the scattering angle in terms of the impact parameter, $b$, ther reduced mass $\mu$, the relative speed $v$, and the scattering angle in the ZMF. Hence show that the ... | g16379 | [
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-0.03... |
<p>An elastic band is stretched using a known force and then placed around a cylinder. How are the forces or tensions distributed? I assume there will be two components: firstly, a tangential or circumferential component, and secondly, a radial or centripetal component. How are these components calculated?</p> | g16380 | [
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<p>I have been puzzled with a fact that as an object moves faster, it ceases its property of opacity. I mean to say that as an object moves faster we can see right through it (more clearly than in a situation when his speed is low). Now with the fact that the speed of light has been controlled upto 61kmph in Bose-Einst... | g16381 | [
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0.03468094393610954,
0.047550126910209656,
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0.048375844955444336,
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-0.006914496421813965,
0.053677041083574295,
0.023563669994473457,
0.024491610005497932,
... |
<p>Does the rotation of the electron around the hydrogen nucleus cause a resultant magnetic field in the atom? If so, the current density must be very high and the resulting field should affect the stability of the atom. How is this field counteracted so that the atom remains stable?</p>
<p>Thanks</p> | g16382 | [
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0.... |
<p>As far as I understand, and from what I have been shown in renderings of <a href="http://cdn4.sci-news.com/images/2013/02/image_907.jpg" rel="nofollow">black holes</a>, they spin (like water going down a drain).</p>
<ul>
<li>My question is, firstly, does the matter being pulled into a black
hole spin?</li>
<li>And ... | g16383 | [
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0.00969722494482994,
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0.012112405151128769,
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0.0453338660299778,
0.023293226957321167,
-0.... |
<p>Consider an elastic collision of a photon with 100 eV energy hitting a mirror. How much momentum is exchanged in the collision?</p>
<p>Also, can one model the reflection of an elastically colliding photon with a single electron in the mirror? It would seem that the photon would be absorbed by the electron, so that ... | g16384 | [
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0.03582875430583954,
0.000738277449272573,
0.0006385408341884613,
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-0.03... |
<p>Assuming a scenario of eternal inflation with a lot of "bubble universes" expanding, Lenny Susskind explains <a href="http://www.youtube.com/watch?v=jnItLp3NR5I&list=EC3E633552E58EB230&index=9" rel="nofollow">here</a> that a potential signal of a collision of our universe with another bubble could be a spot ... | g16385 | [
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0.011003589257597923,
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0.06407321989536285,
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0.0... |
<p>Assumption: The only lights I have are candle, table lamp, and sunlight.</p>
<p>What would I need to create <em>visible</em> reflection of an object in the shallow water contained in a 5 liter bucket? Is it even possible anyhow?</p>
<p>What kind of light out of the three will maximize the visibility of the reflect... | g16386 | [
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0.0... |
<p>If you are told an image is real and you know it was made by a single optic (either a lens or a mirror), which of the following must be true?</p>
<ol>
<li><p>The image distance is positive.</p></li>
<li><p>The image distance is negative.</p></li>
<li><p>The image is inverted.</p></li>
<li><p>The image is upright.</... | g16387 | [
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0.027027713134884834,
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0.021921342238783836,
0.09050068259239197,
0.0048... |
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