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140,262 questions
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Can a spinning ball bounce off the floor without slipping?

Suppose a ball is dropped vertically downward, but it also given some spin along a horizontal axis. Then when the ball bounces, it will presumably pick up some horizontal velocity. Is it possible for ...
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Does energy conservation apply to Casmir effect?

If you cancel out some quantum field modes using two 'casmir' plates you decrease the average energy density in the region and gain potential energy in Casmir force approximately proportional to the ...
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tensor products of exponential annihilation operators

I'm hoping to use this stackexchange to solve a gate decomposition problem, but I am stumped, so hoping for help. These definitions come from the Xanadu Strawberry Fields whitepaper on Table VI and ...
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Random distribution and probability [on hold]

Consider a rectangle of specified length and width, we randomly distribute $n$ points on it. What's the probability of finding no point in an interval of length $x$ and let the width be fixed as '$w$...
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Equation of State

Given is next relation: $S = a [NVE]^{1/3}$ and $a$ is a constant. I have to find the Equation of state. So I started by using some thermodynamic identities: $\frac{\delta S}{\delta E} = \frac{1}{T}$ ...
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How can I verify/validate a private research? [on hold]

I'm an amateur researcher, who's interested in plasma physics and space weather. I'm trying to find a professional physicist, who would be kind enough, to give me a professional opinion about a model ...
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How long does it take to cool down a drink with ice?

If I have a bottle or container with X fluid ounces of water at temperature Y (say, fridge temperature or room temperature), and I put ice or ice sticks (composed of water) in it that make up Z fluid ...
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What shape of gravity and EM fields would a hollow sphere produce, with what resulting effects upon said structure?

The Earth generates a gravity field based on local mass, but which mostly appears to act as a point source, though local fluctuations in the crust density and mass affect the gravity in a given region ...
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What “manifold in band parameters ” means?

I was reading an article https://arxiv.org/abs/0907.0500 in which they write about manifold in band parameter ,like in first line in my picture , and then they call it band parameter . can some ...
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Why is an action built from superfields guaranteed to be supersymmetric?

Given a superfield (in 0+1 spacetime + 2 superspace coordinates) $$X(t,\theta_1,\theta_2) = x(t) + \theta_i \psi_i(t) + \theta_1 \theta_2 F_{12}(t)\tag{1}$$ and given the standard supercharges ...
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Understanding Bell's Inequality?

I'm struggling to understand Mermin's article "Is the moon there when nobody looks?". Is it possible to reduce the number of measurement modes from 3 to 2? For example, with an experimental setup with ...
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The main question was: A car travelled 50 metres in 5 seconds with constant acceleration and initial velocity being zero. What will be the velocity after 15 seconds? I tried to solve by this way, $... 0answers 15 views Dimension of distance travelled in$n$th second and velocity [duplicate] Why is the dimensional formula of distance travelled by a particle in nth second of time same as that of velocity? It's really confusing for me to understand this, after all it's distance but still ... 0answers 17 views Where does differntial equation of covariance matrix come from? Does anyone know where the differential equation of covariance matrix comes from? $$\frac{dC(t)}{dt}=AC(t)+C(t)A^T+D$$ where C is the covariance matrix, ... 0answers 14 views Turing Pattern wavenumber I don't know the relation between the experimental wavenumber that I can obtain from the Fourier spectrum of the simulated pattern and the theoretical critical wavenumber that gives me the linear ... 1answer 27 views Why is it so that some of the paper pieces get stuck to it while others drop instantly when they stick? When we rub a comb on our head and held it near pieces of paper then they get attracted because of induced opposite charge. 0answers 19 views Does water have a minimal thickness because of van der waals force? I have read this question: The thickness of a puddled sheet of water https://en.wikipedia.org/wiki/Surface_tension#Puddles_on_a_surface The liquid mass flattens out because that brings as ... 1answer 68 views Explain the last paragraph of this text First, look at the first paragraph of the second page. It says: The things that you can see at some time are the inside of the light-cone at o. I don't get it. Suppose an event happened outside ... 1answer 18 views Regd. derivation of some equations in “Bertrand Spacetimes” by Pelick We are going through "Bertrand Spacetimes" by Dr Perlick, in which he first gave the idea of a new class of spacetimes named as Bertrand spacetimes after the well-known Bertrand's Theorem in Classical ... 2answers 38 views Black spot when switching intensity of light Whenever I look at a bright light source and then turn my eyes away I see a large black dot blocking a part of my vision. Does this has something to do with Physics as it involves light or it is ... 2answers 40 views Change in kinetic energy of pendulum "An object of mass m is tied to a string of length L and a variable horizontal force is applied on it which starts from rest and pulled slowly until the string makes an angle$\theta$with the ... 0answers 33 views Mathematical Model for a Pendulum in an Electric Field I am studying Higher Level Physics and for my Physics IA I am doing an experiment determining the effect of the voltage between two parallel plates on the on the frequency of a pendulum in between the ... 0answers 9 views Quantum Fisher information for Gaussian states without eigenproblem? Given a Gaussian-preserving interaction (including a unitary operation and losses) for a Gaussian input, I want to know if there is an "easy" way to compute the Quantum Fisher information without ... 0answers 30 views Time needed for an electron to move 15cm An electron has a speed of$2\cdot10^4 m/s$, then it goes inside an electric field$\vec{E}=900 N/C$with direction to positive Y-axis. Without considering the weight force of the electron, the time ... 0answers 40 views Is there any reason that Landau and Lifshitz don't discuss Noether's theorem in their mechanics book? [on hold] I'm currently working my way through the Course volume one. Unless I've completely missed it, the authors omit any discussion of Noether's theorem, instead deriving various conservation laws on a case ... 1answer 33 views Intuition on the overall entropy increase caused by heat transfer Let's say that Hotter Gas A loses heat to Colder Gas B. Heat is transferred from A to B in such a way that the overall entropy increases. This can be proven with equations, but what is the intuition ... 0answers 14 views Connecting two reservoirs When we connect two reservoirs kept at$\mu_{1}$and$\mu_{2}$respectively the potential difference is given by$(-e) V=\left(\mu_{1}-\mu_{2}\right)\$. While if the conduction of electrons occurs ...
We write rms formula as $$v_{rms}=\sqrt\frac{\int_a^b[f(x)]^2dx}{|b-a|}$$ I know if we take arithmetic mean average voltage will be 0. So we want all voltage values to be positive. Why don't we do ...