All Questions

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0answers
4 views

Why does electrostatic potential inside a conducting spherical shell seem to violate superposition principle?

If I want to find the potential at the centre of a conducting spherical shell. The conducting shell bears a total charge of $Q$. The shell has a radius $R$, and there is a point charge of magnitude $...
1
vote
1answer
6 views

Calculating refraction between numerous mediums

I don't consider myself as a good physics student, so sorry if my question is completely stupid. Also I'm not a native English speaker, so sorry if I use the wrong terms, as we learn them differently. ...
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0answers
1 view

Reverse bias under 0.7V

Assume we have a diode.Well I was wondering what is happening if we connect the negative terminal of the battery to the p type region and the positive terminal of the n type region to the positive ...
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2answers
6 views

Location of free charge in dielectrics

I'm going through the introductory section to Electrostatics in Materials in Griffiths, and I have a question that I can't seem to find a satisfactory answer to. If I have a dielectric with free ...
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0answers
15 views

Most influential theoretical physicists of the last decades?

as a mathematician I am interested in understanding as much as posible of the last works in theoretical physics (more precisely the different ways of unifying GR and QM). Who are the most influential ...
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0answers
8 views

Can a pressure wave induce pressure in a liquid it's propagating through?

I have a piece of cylindrical plastic container containing a liquid and sealed at all ends. The bottom seal is a flexible material that can be broken with enough force. The question is then is: can I ...
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0answers
5 views

Scale factor at surface of last scattering

Is there an exact theoretical scale factor associated with the CMB? More specifically, since the CMB is associated with a temperature of around 3000K (as I understand), is there an exact thermodynamic ...
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1answer
28 views

A circular motion problem

A car goes on a horizontal circular road of radius $R$, the speed increasing at a constant rate $\frac{dv}{dt}=a(constant)$. The friction coefficient of the tyre is $\mu$. Find the speed at which the ...
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0answers
4 views

Diffraction Gratings Composed of Spherical Particles (such as those in opals)

I was curious about simulating opals, and after some research, found that their amazing colors come from diffraction gratings. Although, it seems to be different from the gratings caused by what is ...
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0answers
3 views

what will be the Wigner function of N number of coherent states with equal phase difference situated on the circumference of circle?

The number of coherent states are even. All have the equal phase difference. Radius of the circle is defined by the coherent state parameter i.e |alpha|.
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2answers
25 views

Wave function collapse and a general wave function

Action of an operator on a state vector collapses the wave function to any of the eigenstate of that operator , So we get resulting state of the system as some base ket. But mathematically action of ...
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0answers
18 views

Correlated quantum systems

I am working on correlation in quantum systems and would like your comments regarding correlation in quantum systems and to fill the gap in the proofs or to use another type of such relations with the ...
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0answers
19 views

Energy momentum tensor of EM field written in symmetric form

I'm reading A. Zee's book, Einstein Gravity in a Nutshell. In problem 7 of chapter IV.2, it is said that the energy momentum tensor of the electromagnetic field \begin{align} T^{\mu\nu}=\eta_{\lambda\...
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0answers
19 views

How to derive the analytical expression for the retarded Green's function with quadratic Hamiltonian?

For two operators, $A(t)$ and $B(t)$ the retarded Green’s function is defined as \begin{equation} G^R(t,t') \equiv \langle \langle A(t)|B(t) \rangle \rangle^R = -i\theta(t-t')\langle \{A(t),B(t')\} \...
0
votes
1answer
30 views

Where does the kinetic energy of an object annihilated in a matter antimatter reaction go?

A bullet is moving at $0.99 c$. Now we annihilate it by having it collide with an equal mass of antimatter. (assume instant and perfect reaction) This will turn both bullet and antimatter into photons....
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0answers
22 views

Camped - free wing model, including propellers

Good morning, I am modeling a wing structure with an arbitrary number $N$ of propellers. I want to write te equation of motion and the boundary conditions using the Virtual Work Principle. Every ...
0
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1answer
18 views

Qualitative Argument in a Projectile Motion Question

Essentially, my qualms are with Part (a). The argument I’ve come up with are as follows: The ball was launched perpendicular to the plane. That means that the launch angle, which is the angle with ...
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0answers
7 views

How to calculate Average Electric Field for a microscopic filed in dielectric?

In Griffith's book in The chapter of Electric Fields in Matter (The field inside dielectric) , He has considered the Sphere of Radius R and for the inner dielectric element He used the field as $$\...
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1answer
40 views

Does it make sense to speak in a total derivative of a functional?

I would like to consider the problem of the total derivative of a given functional \begin{equation} \mathcal{L}\big[\phi\big(x,y,z,t\big),\theta\big(x,y,z,t\big),x,y,z,t\big],\tag{1}\label{eq0} \end{...
-1
votes
1answer
49 views

Proof for $\langle i[A,B]\rangle$

I have to prove the following equation: $$ \langle i[A,B]\rangle = 2\mathfrak{Im}\left[\int dV(\overline{B\psi)}(A\psi)\right]\,,$$ where A,B are hermitian operators. Here is my calculation, but I don'...
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0answers
13 views

How is a proton beam separated into bunches in a particle accelerator?

I was wondering how exactly is a proton beam separated into bunches, each at interval of 25ns after the previous?
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2answers
28 views

Magnetic field of long cylindrical wire

i have been studying electromagnetism on my own and I got a question about an exercise in David Griffiths, Introduction to Electrodynamics book. So I'm asked to calculate the magnetic field both ...
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1answer
36 views

Is this physics youtube video misleading? (Motional EMF)

I apologize that this is a not a normal post (i.e. not using MathJax but instead posting a video). https://youtu.be/Wgtw5lPKFXI?t=401 In this video (timestamped properly) the physics teacher claims ...
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3answers
302 views

Does the universe have a fixed centre of mass?

Does the universe have a fixed centre of mass? If it does, doesn't it necessarily mean that every action of ours has to be balanced by a counteraction somewhere in the universe so as to neutralize the ...
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0answers
11 views

Simple Electric Motor Didn't Working [on hold]

So I'm making a simple electric motor using 9V battery as power source for my final project. The problem is my motor wont spinning at all. I've scrapped both sides to exposed the wire but it still ...
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0answers
18 views

EM- waves in anisotropic medium

When ElectroMagnetic waves from vacuum enter the anisotropic medium. If the $\epsilon$(permittivity) matrix is diagonal (with not all diagonal entries being equal). There'll be two waves in the ...
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1answer
22 views

Terminology: can I use the world “comoving” to describe a reference frame in which a certain object is at rest?

Here a question about terminology. Suppose I have a particle that is moving at velocity $\beta$ in the observer (or laboratory) frame. Now, is it appropriate / legitimate to describe the frame in ...
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0answers
16 views

Effect of variation in day length on timekeeping

I was reading about atomic clocks when I came to know that precise measurements of time have shown that the time for earth's rotation is slightly more that 24 hrs (on the order of 10^-3). I was ...
-3
votes
0answers
18 views

Dynamics - Masses on Inclined Planes [on hold]

Calculate the coefficient of friction between the block and the ramp if the block reaches a velocity of 0.45 m/s at the bottom of the ramp. Given values: Block has a mass of 60 kg The inclined plane ...
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0answers
8 views

How does signal and background depend on declination

Considering a neutrino telescope, such as the ANTARES, how is the signal and background dependant on the declination.
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0answers
9 views

What is the relationship between Gravity and the Higgs Field/Higgs Boson? [duplicate]

During a talk with my friend, I came up with a question that seemed to spawn too many sub-questions, none of which we could find the answer to online. Nowhere. The [important] questions are: Since ...
4
votes
3answers
284 views

Inverse square law not accurate for non-point masses?

It would seem that the inverse square law, popularized by Isaac Newton, is only true for masses which have no dimensionality and are a single point. In other words, it is only an ideal, not a ...
-1
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0answers
22 views

Acceleration of a pulley [on hold]

In the figure shown, m1=1kg, m2=2kg, m3=0.5kg and m4=4kg. On solving, I observe that the pulley P accelerates downwards. Why does that happen when P has lesser mass hanging from it than Q does? The ...
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0answers
29 views

How to understand notation in “Introduction to Quantum Mechanics (3rd Edition)” by David Griffiths, Chapter 3.6.2?

In the 3rd edition, on page 118, the projection operator is introduced as $$\hat{P}=|\alpha\rangle\langle\alpha|.$$ Then Griffiths says that when $\hat{P}$ acts on another vector, it looks like ...
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0answers
22 views

De Sitter spacetime affine parameter

I am reading Chapter 8 in Carroll's "Spacetime and geometry " textbook and I was lead to exercise 8.2, given as: Consider de Sitter space in coordinates where the metric takes the form $$ds^{2} =...
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0answers
17 views

An empirical formula for cosmological constant [on hold]

I found an interesting empirical formula to get a very close value to the cosmological constant in reduced Planck units. $$\Lambda \approx \frac{2^2}{3^{2^{2^3}}} = 2.88\times 10^{-122}$$ The ...
2
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4answers
76 views

How much of the proton's mass is due to the Higgs field?

The proton mass is 938 MeV. People often claim that (A) The proton is a bound state of two up quarks and one down quark, with the three quarks contributing a total rest mass of $2 \times (2.2 \text{...
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1answer
14 views

Thermal Equilibrium in bucket water with Al piece

Sorry in advance for the poorly formulated title. I am currently going through some assigments in Phyics and came across this one: Question: The heat capacity of a bucket is 1200 J/K and contains 2,...
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0answers
29 views

Why is $\frac{du}{d\phi} = \frac{1}{D \cdot tan(\alpha)}$?

I've started reading this paper where it describes light trajectories on a Schwarzschild spacetime and stumbled upon the following formula: $$\frac{du}{d\phi} = \frac{1}{D \cdot tan(\alpha)}$$ ...
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0answers
19 views

Can water be made more violet?

Water is intrinsically blue because of molecular vibrations. The topic is covered here: Only sea water appears blue in color, why this is not happening in river water? And here, which I post ...
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2answers
22 views

Why do 2 charged conductors gain same potential when connected via wire

Why do 2 charged conductors gain same potential when they are connected via a wire.Can somebody also give a mathematical proof of it?
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0answers
15 views

Potential flow around a sphere [on hold]

I have a problem understanding a example of the book Fluid Mechanis by Landau, 2nd edition, Chapter 1. Ideal fluid- Potential flow, page 22. I need intermediate steps of the problem, I do not ...
0
votes
1answer
20 views

Could the Universe have a finite number of states?

I think most people would say the Universe is infinite, and the number of ways of arranging infinite particles in infinite space is infinite. But we know the "visible" Universe is finite, there is a ...
0
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2answers
38 views

Do electrons contribute to the overall specific heat capacity?

Do electrons contribute to the overall specific heat capacity? Please explain why and why not. I researched for a bit and most of them said mostly phonons contribute to the specific heat but never ...
0
votes
1answer
19 views

Formula manipulation

What is the potential energy of a metric ton (1000 kilograms), 3 meters above Earth's surface (at sea level), expressed in Kilowatt Hours? Assume that the mass will end travel when it contacts Earth. ...
0
votes
2answers
44 views

Can someone explain the $ttH$ Coupling?

IS the $ttH$ an actual particle? If so, how can it form? I though the life of the top quark was way to short to form a particle. If it is not a particle, what is meant by coupling.
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0answers
20 views

Can humans detect the original gravitational waves?

How far is the universe's original gravitational wave propagation?
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0answers
14 views

If not the conjunction moon, then what? [on hold]

It was either 2017 or 2018, I don't remember the season, I didn't really think much about it, but I was driving in the Finger Lake regions of NY, Cayuga lake to be exact, It was still dark out, I left ...
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0answers
20 views

Young's Double Slit, phase difference and path difference

To produce an interference pattern, the light sources must be coherent right? Coherent by definition means constant phase difference between waves of the same frequency so that means waves can be ...
0
votes
2answers
31 views

Impulse on a Gyroscope

I've been studying gyroscopes, and I understand why a fast spinning gyroscope doesn't fall. However, I don't understand why a slow spinning gyroscope does fall, or why a large enough impulse to a fast ...

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