1
vote
0answers
5 views

How do we force a turbulent fluid to keep the input energy rate equal to energy dissipation rate?

If I want to do a DNS (direct numerical simulation) for turbulent fluid, and I know $\nu$, how can I add an external force so that the input energy rate is equal to the energy dissipation rate? If ...
1
vote
0answers
7 views

Hamiltonian for a Lagrangian with coupling

I am dealing with the following Lagrangian density $$\mathscr{L}_{em}= -\frac{1}{2}\rho\omega^2 u^2 +\frac{1}{2}\nabla u:\Sigma :\nabla ...
0
votes
0answers
6 views

Pressure Coefficient on fluid mechanics

I have to solve numerically a fluid mechanics problem. I have one airfoil with a flap deployed downwards. Under the airfoil I have set a mesh with some nodes. I have already computed stream function ...
2
votes
2answers
25 views

Higher rank $\gamma$-matrix question

I am reading that the higher rank $\gamma$ matrices can be written as alternate commutators and anti-commutators. For example the the rank 3 gamma matrix can be written as $$\gamma^{123} = ...
0
votes
2answers
14 views

How is energy transferred in Joules law of heating?

Joule's law of heating states that an accelerated electron loses its energy, which is then converted into heat energy, by colliding with vibrating atom i.e ions in their lattice site. but we know atom ...
0
votes
1answer
20 views

How one can know the gauge field emerging from the local gauge invariance is actually the EM field?

How one can know the gauge field emerging from the local gauge invariance is actually the EM field? I understood in a simple scalar field whose Lagrangian is given by $ \mathcal{L} = ...
1
vote
2answers
19 views

How to reconstruct the dependence of the potential from a coordinate?

What is known is that an ion sent along the X-axis of a black box with a speed $V$ returns in the time of: $$T=a V^b$$ $a$ and $b$ are some known constants. Having this, can we reproduce the ...
0
votes
0answers
15 views

Interference of sound: how to calculate the sound intensity at each point?

I need help with the following question: Two speakers are sending out sound in phase with the frequency 2,13 kHz. The sound from the speakers is registered in three points A, B and C. See figure. ...
3
votes
2answers
43 views

How to find the center of mass of several objects in a 2d plane?

We have the following scenario in a 2d plane: a big rectangle with a lot of smaller similar uniform rectangles in it, all of them weight differently. Where is the center of mass of this object ...
-2
votes
0answers
29 views

What collapsed the wave function of organic molecules for life to form?

The wave function only collapses when it is measured by an observer. So, before life came into the universe, I'm guessing that everything existed in superposition. We are told life was formed as a ...
0
votes
4answers
27 views

What happens when I place an object of certain temperature in space ? Does it loose its entire heat energy?

Can i obtain absolute zero temperature this way? And let's assume there is no cosmic microwave background and also assume that there is a way to shield the object from any heat source, such as the ...
1
vote
2answers
152 views

I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator?

I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator? The tree wasn't wet, either and it was a pretty strong shock ,too.
-2
votes
0answers
35 views

Discharging an electric field

Is it possible to discharge an electric field without removing the power source? I understand that electric fields have a positive charge so would it be possible to use an earthed coil to discharge ...
0
votes
1answer
33 views

Is nature quantized?

I was reading Planck's postulate the other day on Wikipedia and couldn't help but noticing the sentence: "...is the postulate that the energy of oscillators in a black body is quantized..." ...
-2
votes
3answers
41 views

Can you die from a $250 \, \mathrm V$ broken cable? [on hold]

I have a laptop power cable that is broken, my dad taped it so it is safe now. I am just wondering: would it have killed me had I touched it? If you could state your qualification/job to show you ...
1
vote
3answers
24 views

Do components of force have direction when doing work?

When we get angle > 0, the x-component of force is along the direction of displacement and so their product is called Work. So the x-component of force is said to have direction of the respective ...
1
vote
3answers
31 views

Cause of rolling friction

Can you explain the cause of rolling friction? Can you tell me why, while driving a bicycle, there is less rolling friction when its tyres are fully inflated?
0
votes
0answers
14 views

Oscillators with anharmonic interaction terms

I'm looking for papers modeling oscillators coupled with anharmonic interaction terms. The term is combination of a linear element and a Gaussian kernel that decays proportionally to the difference of ...
0
votes
0answers
19 views

Magnetic field due to wire and plane [on hold]

Suppose we have a wire with some current $I$ and which at a point $o$ spreads radially in all direction along conducting plane perpendicular to wire so what will be magnetic field at above and below ...
0
votes
0answers
12 views

In MWI, how to make sense of the nonuniqueness of decomposing mixed states into pure states?

It's well known that in quantum mechanics, a generic mixed state can be decomposed into pure states in infinitely many different ways. While this property is kind of understandable if quantum states ...
0
votes
0answers
17 views

Dependence of kinetic friction on relative velocity

While I was reading my book I came across a line that tells that there is slight dependence of kinetic friction on velocity of relative motion of the bodies. Can anyone tell me how is this so?
0
votes
2answers
49 views

Can gravitational constant be changed?

In my book(Principles of Physics by Resnick,Halliday,Walker) , the authors write: If $G$ - by some miracle - were suddenly increased by a factor of 10, you would be crushed to the floor by Earth's ...
0
votes
1answer
20 views

How does resonance store vibrational energy?

In the wiki article, it is written that in resonance, maximum amplitude is possible as vibrational energy is stored. What does that statement mean? How is energy stored so that max. amplitude ...
1
vote
1answer
25 views

Polarized light

A light is made up of electric and magnetic fields oriented perpendicular to each other. Can polarization lead to the removal of any of the field completely?
0
votes
1answer
16 views

Ability to discharge static electricity

Ever since I was a child, I have been able to "discharge" static electricity in clothing by touching it. The static falls out immediately! As a child my mother would have me touch all the laundry ...
1
vote
1answer
27 views

Question concerning the diagram for stress tensor

I have a couple of questions related to the diagram in the answer by Kyle Kanos to this question, Why is stress a tensor quantity?. Q1. If the box shown is of finite size why are there not three ...
0
votes
1answer
34 views

How experimentalists put bounds on new physics at the LHC?

I would like to understand how experimentalists search for new physics at the LHC. Lets imagine I want to use the LHC data to put a bound on the coupling of some new physics effective operator, say, ...
0
votes
0answers
26 views

Upper division physics lab — Project ideas [on hold]

As an experimentalist, I am very excited to be taking my first upper division physics lab next semester! The course covers basic electronics (filters, diodes, transistors, op-amps, analog & ...
0
votes
0answers
20 views

Frictional loss of matter

How do we account for the loss of matter from an object due to friction ? Is it simply a phenomenon or result of any other process ? Eg :The loss of matter from the rubber tyre
0
votes
0answers
7 views

How do you work out the energy requirement for a submerged pump?

I was wondering if you were to place a pump in a submerged container and then were to open a hatch allowing water to flood the previously vacant cavity how much energy would be required to discharge ...
0
votes
0answers
10 views

What is trivial and non-trivial gate in computing?

My question seems like it should be posted in Computer Engineering section, but below is how I found this word. I was reading the textbook: Quantum Computation And Quantum Information - by Michael A. ...
3
votes
1answer
58 views

Are fundamental forces always attractive/repulsive, i.e. parallel to the separation?

If magnetic monopoles existed it would not be the case - the forces on an electron and a magnetic monopole passing by each other would be at right angles to the vector connecting the two particles! ...
2
votes
0answers
35 views

Lorentz transformation - Bjorken & Drell

I'm trying to derive (14.25) in Bjorken & Drell (B&D) QFT. This is $$\tag{14.25}U(\epsilon)A^\mu(x)U^{-1}(\epsilon) = A^\mu(x') - \epsilon^{\mu\nu}A_\nu(x') + \frac{\partial ...
0
votes
1answer
22 views

What unit of distance to use when calculating power loss?

80% of Earth's atmosphere is within 10 miles of Earth's surface. I know that power attenuates inversely as the square of the distance within the atmosphere so it occurs to me that a 50,000 watt signal ...
-1
votes
3answers
61 views

When we catch a falling object, where does its kinetic energy go?

Some of it is transformed into heat and noise, but where does the rest go? Further details: The object does not bounce off (e.g. a sack of rice marble ball). The hand remains completely static ...
0
votes
1answer
39 views

How do gravitons couple to the Stress-Energy tensor?

How do gravitons couple to the Stress-Energy tensor $T^{\mu\nu}$? How did physicists arrive at this result? I've read that it follows from the analysis of irreducible representations of the ...
-1
votes
0answers
36 views

Double slit experiment setup which resolves dualism

Suppose we have the following setup of double-slit experiment: A point source of coherent photons emits them so that they fall onto a non-transparent panel D ...
0
votes
0answers
27 views

work done for time dependent Hamiltonian

I want to calculate work done by external force when my Hamiltonian is described by $$\hat{H} = \hat{H}_{0} + F(t)\hat{A}$$ According to First law of termodynamics $$dE = \delta W$$ so, $$E = ...
0
votes
0answers
23 views

Can the strong force be explained by quaternions?

I wonder if the strong force can be explained by quaternions without the use of matrices. I heard that it could, but the source was not reliable.
3
votes
1answer
92 views

Light in a box with positron walls instead of electrons

I understand that with a hollow cube with the inner walls covered in mirrors given a light source briefly, the light would eventually be absorbed. This is due to electron excitation I believe. So ...
0
votes
1answer
89 views

Is imaginary time a fifth dimension? [duplicate]

I've read that by introducing the concept of imaginary time, the dimension of time can be treated like a spatial dimension mathematically. Assuming, without imaginary time, one considers the universe ...
2
votes
0answers
39 views

Time functions in general relativity

In my general relativity notes a function $f$ is called time function, if $\nabla f$ is time-like past-pointing. Say that we are in Schwarzschild spacetime and I want to check if $f=t$ is a time ...
0
votes
2answers
42 views

Photon walk in stars with convection

I'm having trouble figuring this out. I've read, that when photons are created via nuclear processes inside a star, it can take about 1 million years for photons to actually reach the surface of a ...
-1
votes
0answers
36 views

How to derive the light pressure from maxwell equations? [on hold]

Is there any reference? Was the idea of radiation pressure known to Maxwell himself?
-1
votes
1answer
31 views

Projectile at an angle. Finding the angle using conservation of energy [on hold]

Ball is thrown at an angle α and at the highest point it's potential and kinetic energy are the same. Find the angle. Use the law of energy conservation. What the professor wanted $mV^2/2 = 2* ...
1
vote
1answer
57 views

Turning off point for 1g acceleration

Let's say I am on a ship accelerating with 1g. I want to keep the engine running for half a year ( to an observer from my point of origin ) but due to time dilation it would have to be sooner than ...
-4
votes
1answer
35 views

Does light or waves have any kind of mass? [duplicate]

Just like the previous question, Even I have been studying Hawking's A Brief History Of Time and even I was thinking of Einstein's General Relativity. But I was unable to accept his view of GRAVITY. ...
6
votes
1answer
38 views

Twin paradox, different starting locations

Let's say I have a twin who is at rest relative to myself and ten light years away from me, we are both in rocket ships. We have agreed that I will send a laser pulse and that when he receives it we ...
0
votes
1answer
62 views

Do paradoxes exist due to velocity addition?

Do paradoxes exist due to velocity addition ? .. In the above diagram, we have a very lengthy 259,627.885 km long space station. Rocket "A" is parked at the left end of the space station. Let us ...
0
votes
2answers
35 views

Would an airtight box filled with air act the same way to 1 bar of water pressure as the same box vacuum-sealed at atmospheric pressure?

Pressure On average, a column of air one square centimeter in cross-section, measured from sea level to the top of the atmosphere, has a mass of about 1.03 kg and weight of about 10.1 N (2.28 lbf) ...

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