# All Questions

127,765 questions
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### Biophysics Concentrations homework question, Question (a) and (b)

Homework Problem for biophysics course I honestly am not sure how to proceed to determine the concentrations, the only hint professor gave me was to use equilibrium K and the fact it was neutral to ...
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### From XFlow CFD to Hololens/AR

I have to export a mesh plus computational data from XFlow and put it on a HoloLens device to show how a meshed object with a steam flow on it appears in an augmented reality environment. Can you help ...
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### Strain Rate Tensor and Rotation Tensor

How can I prove that $S_{ij}$ (strain rate tensor) is zero for the ﬂow ﬁeld $u = U + \Omega \times x$ , where $U$ and $\Omega$ are constant linear- and angular velocity vectors by using Cartesian ...
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### Could Dark Energy actually be gravity from unimaginable mass outside our universe?

If there is a huge amount of mass outside of our observable universe, could that explain the universe expansion?
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### Yet another kinematics question with non-uniform gravitational acceleration [on hold]

A problem is posed where an object is launched into the atmosphere from the surface of the earth at such an initial velocity that it comes back to the surface of the earth after a specific time t. ...
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### Why is the laboratory frame energy always greater than the center of mass frame energy?

I have been looking for an answer to 'Why is the laboratory frame energy always greater than the center of mass frame energy during collisions?'. A lot of resources provided mathematical explanations....
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### Do charges in a metal group up a little in the middle?

Around the edges of a metal, the density of electrons is higher than the rest of the metal. I think this is because every electron is surrounded by neighbours pushing them away but once you get to the ...
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### Motion and velocity

A body at rest is given an initial acceleration of 8.0ms for 30 secs after which the acceleration is increased 12.0ms for the next 20 secs the body maintained the speed attained after which it is ...
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### How does an initial velocity affect the tangential velocity when a rocket cross the poles?

I'm trying to improve a piece of code I've written to allow for shooting rockets across the poles while being affected by the coriolis force. The code is written using RK4 since we are also looking at ...
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### I need to find the drag coefficient of a pendulum bob

Is it possible to find the drag coefficient of a pendulum bob from the damping caused on it during swinging. I will be able to measure its displacement from the point of origin and plot it against ...
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### Calculating the peak-to-peak range of sinusoidal variation in noisy data; phase-sensitive detection

I have a problem in a set of questions on elimination of noise and phase sensitive detection for which I have an attempted method but the answer does not match the suggested numerical answers, and I ...
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### Temporal Phase, Spectral Phase, Total Phase…

I am a little confused about the phase in the electric field as a solution to the wave equation. Phase $\phi$ The solution to the wave equation we get from Maxwell's Equations is the real-valued ...
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### Mean field 3d Ising model in Landau theory

I am solving a problem for some course I am following. I am given the Hamiltonian: $$H = 3NJ \langle \sigma\rangle ^2 -6J\langle \sigma\rangle \sum_i\sigma_i,$$ where $i$ sums over all sites ($=N$)....
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### How to derive the hamiltonian of general relativity (ADM formalism without surface terms)?

given that $ds^{2} =−N^{2}dt^{2} +h_{ij}(dx^{i} +N^{i}dt)(dx^{j}+N^{j}dt)$ $S=\int dt d^{3} x\sqrt{h} N(^{3}R+K_{ij}+K^{ij}-K^{2})$ where $(^{3})R$ is the Ricci scalar of hij, h the determinant of ...
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### Could the theory of everything be an algorithm?

I've been thinking about the theory of everything. Could the theory of everything to explain how the universe work be a computer algorithm? Is there any way to test whether the universe is a ...
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### Questions on velocity that are multistep? [on hold]

I know these may seem simple but I'd really appreciate how to proceed with these questions. A plane takes off from JFK heading towards Miami, which are 1765km apart. The entire trip takes 5 hours. ...
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### Mode in quantum mechanic

Let suppose we have $N$ identical composite particles at ground level. Each composite particle have two distinguishable particles. Thus the state of composite bosons in ground state can be written as ...
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### What is the wave nature of electron? [duplicate]

Is electron a standing wave or a probabilistic wave? or is it both? can someone explain me also what wavelength we calculate from de Broglie's equation? also does electron spin around itself? or is ...
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### Have we really reached moon? [on hold]

it seems like NASA and other space agencies are making fool of the whole world. i think that they are showing us just fake photos of them going there. ???? i don't know much about stack exchange , so ...
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### Max Planck and energy quantization idea

Did Planck have an intuition behind the idea of energy quantization of atomic oscillators and radiation, or it was just a mathematical trick to drive his distribution law?
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### Gyroscope precession direction of torque

On the opposite side of the rotation vector direction [L], when i applying force upside of rotor surface(dotted line) Why the generated torque cause the rotor to rotate counterclockwise? when i apply ...
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### Attributes of the arrow of time

What are the elementary attributes of the arrow of time? The connection of entropy as a causality of the arrow of time has been logically excluded (reference available on request). Are there other ...
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### Relation between height and range

The height of water level in a tank is H. The range of water stream through a hole at depth H/4 from upper water level will be.
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### What is the physical meaning of static and velocity pressure?

According to Bernouli's equation, the static pressure inside a pipe with streamline and steady flow decreases with fluid's velocity. One explanation to rationalise this phenomenon is because velocity ...
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### Why use $\ln$ in definition of pseudorapidity?

Why is pseudorapidity defined as $\eta = -\ln[\tan(\frac{\theta}{2})]$ as opposed to just $\eta = \tan(\frac{\theta}{2})$?
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### According to general relativity, why are two objects at rest attracted to each other? [duplicate]

I'm trying to understand gravity in General Relativity and I'm having some questions. I can understand that an object in orbit around another more massive object is free falling and simply following a ...
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### Double Slit vs Diffraction Grating Intensity Graph

I had a few questions regarding the intensity graphs of fringe patterns observed when light is shone through a double slit vs a diffraction grating. For a double slit, does the intensity of the ...
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### Interesting “paradox” from class: Impulse on a rod in a vacuum results in different energy in dependence on point of impulse

This question has been somewhat addressed here, but the discussion ended a little too soon in my opinion. (Sadly, I cannot simply comment in the thread due to low reputation). Say we have a rigid rod ...
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### Can the electromagnetic radiation pressure $p=u/3$ be the thermodynamic one $p(T)=u(T)/3$?

Can the electromagnetic radiation pressure $p=u/3$ be the thermodynamic one $p(T)=u(T)/3$? In electromagnetism, the radiation pressure formula $p=u/3$ does nothing with temperature at all. One quick ...
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### How can a vortex be created?

i have seen this video. https://www.youtube.com/watch?v=pnbJEg9r1o8&t=96s It is not completly clear how a difference of velocity can cause a vortex, can you explain me?
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