All Questions

0
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0answers
3 views

Potential Flow integration [no-voice and very beginner!]

Let's say I managed to compute a velocity field that is divergence-free. How do I integrate it over time? meaning, I created a potential function, set v to be curl of potential function, so I have now ...
0
votes
1answer
20 views

What would the effects be on the world if light slowed down?

It would be really helpful if the effects were just given in a list form so I can research them. The reason why I am asking this is because I to write an essay regarding the effects of a change in a ...
0
votes
1answer
22 views

Physics theory/concept behind this question

The question is: Two cars start off at the same location and move away at constant velocities. At t = 0 s car A moves away with a velocity of 12.5 m s−1 NORTH and car B moves away with a velocity of ...
0
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0answers
13 views

Can Mars have an oxygen atmosphere?

It is my understanding that, in its gaseous state, oxygen molecules move fast enough to achieve escape velocity. On Earth, we see this more clearly with helium. Regardless of what's happening on ...
0
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0answers
9 views

Why parity required simmetry)

I'm studying parity for the first time but there is something I don't understand. I read that a system conserves parity if every experiment is the same in a mirror that is also 180 degree flipped. ...
0
votes
1answer
17 views

How to Construct Proper Spherical Coordinates in Minkowski Spacetime?

In $n$ dimensional Euclidean space, we only need one radial coordinate, and $n-1$ angular coordinates, where one ranges from $[0, 2π)$ and the rest range from $[0, π]$ Spherical Minkowski coordinates ...
2
votes
1answer
42 views

Problems of Klein Gordon equation

Consider the Klein-Gordon equation $$(\square+m^2)\varphi=0.$$ People usually claim that $\varphi^* \varphi$ cannot be interpreted as a probability density because $\int d^3\vec{x}\varphi(t,\vec{x})^*...
0
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0answers
14 views

How much more damage is caused after hitting a brick wall at 100mph over 50mph? [duplicate]

How much more damage is caused after hitting a wall at 100mph over 50mph? It is clear that there is just twice as much force generated after hitting a wall at 100mph, since the deacceleration is twice ...
1
vote
0answers
21 views

Does Graviton bend light?

In the weak gravitational regime where the low-energy effective action holds,(linearized) gravity can be quantized, and we can treat graviton as quantum fields on a Minkowski background. One can also ...
0
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0answers
9 views

What is the relation between Reflectance and Intensity?

I am just reviewing Fresnel's equations where Reflectance R is equal to R=|r|^2 where r is the complex reflection coefficient. Is there an equation that relates ...
0
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0answers
19 views

Moving a (specific)-spacecraft without ejecting mass

The idea is to move this spacecraft without ejecting any mass. The craft has two paddles which we can make spin. So we rev these two paddles up, spinning them in opposite directions and when their ...
0
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0answers
10 views

What devices are used in a proton accelerator to separate the protons from their electrons and send the protons into the vacuum chamber?

I understand the general idea of how they accelerate the protons once they get them isolated in the chamber, but what's the device they use to isolate them to begin with even called?
0
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1answer
20 views

Prove that the electric field produce by a punctual charge is isotropic and radial

I would like to prove mathematically that the electric field produced by a punctual charge is isotropic and radial, i.e. $$\vec{E}(r,\phi,\theta)=E(r)\vec{e}_r\tag{1}$$ I think that this statement ...
0
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0answers
9 views

Density of states analogue in non-interacting multi-electron atom

I'm reading a paper on optical effects which very early on assumes that there are no interactions. Given that I want to simulate an atomic vapour (modeled, initially, at least, as non-interacting ...
-9
votes
0answers
32 views

QM1223344556666664545 [on hold]

Schrödinger's electron electric wave replaced with an electron probability wave but an electron position probability can only represent a positive value or zero and cannot depict a negative value that ...
0
votes
1answer
21 views

Why current always chose to go to the resistance which is lower

My teacher asked me why currents chose the easy way and he wanted me a mathematical formula about why current always go over a resistance which is smaller
0
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0answers
12 views

Relative velocity and pseudo forces

If I am in a spaceship moving in deep space....... which is accelerating.... There is nothing around to compare my motion with.... How can I say even if I'm moving or not....if I say I experience a ...
0
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0answers
11 views

Can electrical currents be accelerated due to the geometry of the conductor?

If dc current is passed through a section of piping to detect discontinuities, can certain flaw geometry (cracking, porosity) cause an decrease in resistance?
0
votes
1answer
18 views

Luminosity of a white dwarf

I have a very simple question, yet i am confused.Can someone tell me why in an H-R diagram the white dwarfs are at the bottom left? As in I understand that they would have a high temperature when they ...
0
votes
0answers
5 views

Determining the position and spectral weight of Andreev states from a retarded Green Function

I'm trying to understand a result from the paper Josephson current through a correlated quantum level: Andreev states and $\pi$ junction behavior by Vecino, Martin-Rodero and Yetati (2003). ArXiv link ...
0
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0answers
4 views

How to add protective enclosure around exposed thermal camera

First off, let me state that I'm not entirely sure this is the right forum for this question. This was the only section I found multiple questions pertaining to thermal imaging, however, so I thought ...
1
vote
1answer
23 views

Wigner map of the product of two operators

Does anyone know how to prove that for the product of two operators $\hat{A}\hat{B}$ the Weyl-Wigner correspondence reads $$ (AB)(x,p) = A(x-\frac{\hbar}{2i}\frac{\partial}{\partial p}, p+\frac{\hbar}...
0
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0answers
21 views

Is TMPH documented formula useful? [on hold]

In tires manufacturing TMPH is a limit scale and is its own unit, I think the formula was created by Michelin or Bridgestone and it is very similar to the force formula. $$TMPH = Ton Mile Per Hour$$ ...
0
votes
2answers
30 views

Why does current remain same in a series circuit?

Current is the rate of flow of charges with time. When passing through each resistance in a series circuit, charges lose energy and "slow" down due to collisions with atoms (metal cations). When time ...
-6
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0answers
23 views

classical physics, problem number 6

[the question number 6 has to be solved of this given picture] (https://i.stack.imgur.com/yTezc.jpg) please solve the problem as soon as possible
1
vote
0answers
13 views

Why do we need the two higgs doublet model?

Why do we add an extra doublet to the two higgs doublet model?I mean what are the conditions due to which we had to add an extra doublet. What are the limitations with only one doublet and how 2HDM ...
1
vote
1answer
62 views

Schrödinger Equation with Imaginary Potential

I am trying to solve the following equation (in 1D) and stuck in the middle of the way. Here's the equation: $$i\frac{\partial\psi}{\partial t}=C\cdot\frac{\partial^{2}\psi}{\partial x^{2}}+iD\cdot\...
0
votes
0answers
10 views

What happens when a photon hits a particle (radiative heat transfer, photoelectric effect)?

By relating temperature to particle motion, the kinetic theory of gases gives an intuitive explanation of conductive heat transfer; faster particles collide with slower ones to transfer kinetic energy....
0
votes
0answers
10 views

Applying law of biot-savart when magnetic field passes through different materials

Hi Im trying to calculate the power of a magnetic field outside a coil winded around a electric steel core. The point Im trying to measure is on the axis of the coil but 2mm outside the electric steel ...
0
votes
0answers
6 views

Calculating the shielding required to protect against radiation at lunar orbit

I am attempting to calculate the thickness needed to protect the crew inside a space module at the Lunar Orbit with Lithium Hydride from X and Gamma Rays. How would I calculate the thickness of Li-H ...
2
votes
0answers
34 views

What is complex frequency?

I am learning EE, and about complex frequencies, but what is its physical meaning? What is it used for? Why is it? And only happen in the laplace transform?
0
votes
1answer
16 views

How to calculate mass proportions of each compound in air?

We know average volume proportions between compounds in dry air. Here are the more important (in terms of proportions) ones: How can we calculate mass proportions between these gases? I'm ...
0
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0answers
16 views

Warped product manifolds with Ricci-flat Fiber

There are some reason why the Warped product spacetime has been studied imposing the Fiber Ricci-flat?
0
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0answers
27 views

Length Contraction of a rotating object

When observing an object, such as a spinning ring, what velocity is used to calculate its length contraction? I know it depends on the observer, but let's say theoretically an observer is just ...
0
votes
2answers
38 views

What happens to the energy of an absorbed photon?

Photons are electromagnetic wave fields that travel at the speed of light. When they are absorbed by an object, their momentum and energy is transferred to the absorbing object. What is that ...
0
votes
2answers
18 views

Thermal radiations

everything having temperature above 0 k emits radiation. But those radiations depend upon temperature of the body and not on nature of the body. Why thermal radiations are not material dependent?
0
votes
1answer
38 views

Does the heat created by gravitational energy cause Infinite energy?

As everyone knows there is this thing called geothermal energy. Many people in Iceland and such countries get their energy from geothermal plants. My question is since some of the heat in the earth is ...
1
vote
1answer
30 views

Proof of equipartition theorem for $i$ not equal to $j$

The generalized equipartition theorem (where variables need not be quadratic) states that if $x_i$ is a canonical variable (position or momentum variable), then $$\left\langle x_i \frac{∂H}{∂x_j}\...
2
votes
2answers
50 views

Resistance of an object with arbitrary shape

Suppose to have a conductor with a non-trivial geometry, like the one in the picture: The shape does not really matter for this question, as long as you suppose to have at least one "hole" in the $z-...
-4
votes
0answers
17 views

Quarterback Question [on hold]

Quarterback passes football at 8.00m/s at angle of 31.5 degrees above horizontal. How far does it travel horizontally (assuming it is caught at the same height it is thrown)?
2
votes
1answer
99 views

Is it possible to find dry ice crystals lying around the base in Antarctica?

Dry ice sublimates at -78.5°C, while the lowest temperature registered is about -89.2°C around the Vostok station in Antarctica. Imagine a person living on that station on that day (or night, since it ...
0
votes
1answer
6 views

Lateral (bending) stiffness of a helical compression spring

Does a helical compression spring have uniform lateral (bending) stiffness throughout its length? Suppose I exert a force radially along a certain height of the spring, and that force rotates along ...
0
votes
0answers
8 views

Magnetic Dipole Moment of cylindrical current distribution

In this attached image, i have to find dipole moment as it is part of my homework assignment
0
votes
1answer
14 views

How to calculate mass of a gas mixture knowing its volume, molar mass and pressure?

I have a gas mixture of volume $V$, molar mass $m$, pressure $P$. I need to calculate its mass $M$, but all formulas I found get in the loop as pressure formula requires density, which then ...
-3
votes
0answers
38 views

Is it 4-D or 11-D Universe? [on hold]

I know these are just theories, but I wish to know which of the two are the most used right now to speculate how many dimensions of space and time our universe has. I heard that in the standard ...
0
votes
0answers
6 views

Relationship between polarization charge density and free charge density

I have concluded that in a uniform dielectric, volume free charge density $\rho_0$ and volume polarization charge density $\rho'$ satisfy $$ \rho' = \frac{-(\epsilon - \epsilon_0)}{\epsilon}\rho_0 $$ ...
-1
votes
0answers
25 views

Suppose that we are living in an Anti de Sitter space: which open problems would be solved? [on hold]

It is often said that we live in a de Sitter (dS) universe. This is because the standard theory of cosmology is descibed in a four dimensional de Sitter space-time. On the other hand, there are some ...
1
vote
3answers
45 views

Inertial and non-inertial reference frames

My book states that: A reference frame attached to earth is not inertial because it is revolving around the sun and it is rotating about its own axis. Don't we need a specified observer's frame ...
2
votes
2answers
107 views

Curl and circulation of a vector field that is ill-defined at the origin: any interesting physical effects?

In the cylindrical polar $(\rho,\phi,z)$ coordinate, suppose the velocity field in a liquid is given by $$\vec{v}=\frac{K}{\rho}\hat{e}_{\phi}, \qquad K=\text{constant}.\tag{1}$$ It can be easily ...
0
votes
0answers
14 views

How to calculate the transition energy between $^2P$ to $^2S$ and $^2D$ to $^2S$ for sodium?

It's been known how to calculate the Zeeman effect. However how to calculate the transition energy between $^2P$ to $^2S$ and $^2D$ to $^2S$ for sodium($Z=11$)? ($^2P$ here meant term symbol ignored ...

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