0
votes
3answers
94 views

Speed of electricity in cable [duplicate]

Movement speed of electricity in cable, is same as speed of light in space? In other words, electricity moves in usual electro cable aproximatelly 300 000 km/second ?
0
votes
1answer
330 views

What is the initial velocity of an object, given a change in mass, and an exerted force [closed]

An 8.0-g bullet is shot into a 4.0-kg block, at rest on a frictionless horizontal surface (see the figure). The bullet remains lodged in the block. The block moves into an ideal massless spring and ...
1
vote
1answer
88 views

Modeling transient heat transfer between two 1-D materials

So I have been working on creating a 1-D model of a material with a layer of heat resistant material stuck to it. For this I have been trying to use the implicit finite-differential method. The ...
0
votes
0answers
161 views

Alternative expression for Bethe vectors of su(2) XXX chain

As is well known, the eigenvectors of the transfer matrix for the su(2) XXX spin chain of length $L$ are given by acting on the ground state $|\uparrow^L\rangle$ with all spins point up with the ...
5
votes
3answers
491 views

Why don't surfboards fly out the back of a utility truck when driving on the highway?

I have never had it happen myself and every time I throw my boards (shortboards not malibus) in the back of someone's ute, with no cover on the tray, they always assure me they'll be alright( the ...
0
votes
1answer
46 views

Avoiding a singularity in the simulation of a spherica pendulum

I didn't know whether to put this here or in StackOverflow - so I open to answers just telling me to go there! I am looking to simulate the motion of a spherical pendulum. The Lagrangian is $$ ...
4
votes
2answers
211 views

Why is $d^4p$ “obviously” Lorentz invariant?

Is there a mathematical and a physical reason? I believe it follows from the jacobian of the Lorentz transformation. But, if that is so, I don't see why it would be "obvious" unless you can do such ...
11
votes
1answer
272 views

Why is the second law of thermodynamics indisputable? [duplicate]

Why is the second law of thermodynamics undisputable? On his website Professor Hawking says the following: The cosmologist, Sir Arthur Eddington, once said, 'Don't worry if your theory doesn't ...
0
votes
2answers
58 views

Defining charateristic of light wave?

"Light is refracted when it travels from one medium to another." Does the sentence show that light is a wave?
4
votes
0answers
74 views

${\phi}^4$ description of Ising ferromagnet

Suppose the coupling between two spins is $C_{i,j}<0$, then the classical partition function is given by $$Z=\sum_{\{s_i\}}e^{\sum_{i,j}s_iK_{ij}s_j+h\sum_{i}s_i}$$ where $K_{ij}=-\beta C_{ij}$ and ...
0
votes
2answers
264 views

Magnetic flux density of a solenoidal electromagnet

I am designing an electromagnet which will be used to test magnetic sensors. So I used to formula found at hyperphysics which relates the magnetic field flux density to the number of turns, the ...
1
vote
0answers
125 views

Mass, density and gravity for 2D SPH

Having previously only worked with 3D sph, the 2d case is confusing me. The concept of mass and density as well as gravity is not easily converted, as I see it. As an example in 3D I take 1000 ...
0
votes
3answers
278 views

Friction of a rolling cylinder

I was wondering why friction vectors are drawn differently regarding a cylinder rolling on a surface and a cylinder rolling down an inclined surface. Since friction is responsible for the rotational ...
4
votes
3answers
572 views

How to find the direction of an eddy current?

Suppose there is a magnetic field going from left to right. Suppose a thin sheet of metal conductor (e.g. a 1m*1m square) is dropped through the magnetic field such that the plane of the conductor is ...
1
vote
2answers
62 views
0
votes
1answer
66 views

Will the heat flow rate be same when temperature difference is not same?

If I give heat with a certain source will the change of temperature difference change the heat flow rate? Suppose I have a aluminium rod which has a weight of 25 gram. I heated it up to 40 degree ...
0
votes
0answers
51 views

How do chirped mirrors compensate dispersion?

How do chirped mirrors compensate dispersion? I understand that if you have longer wavelengths penetrating deeper into a chirped Bragg stack, then there will be some anomalous dispersion because the ...
0
votes
2answers
161 views

What happens to the kinetic energy of a system in a non-elastic collision? [duplicate]

I know that the kinetic energy of a system is NOT conserved in a non-elastic collision. But energy is supposed to be conserved, so where does all that energy go? Is it transformed into other forms ...
1
vote
1answer
116 views

Switch from the position representation to the momentum representation

If we use Fourier Transform, we can switch from the position representation to the momentum representation, like the following formula here comes the problem, if we use dirac notation we can see it ...
1
vote
2answers
116 views

What's the right way to calculate power consumption over a month given a rate per minute?

When I was searching for power required to lift an object, i found that, for example: $100\ \mathrm{kg}$ to be lifted 3 metres in 5 seconds. (vertical) Answer: $$\begin{align} ...
0
votes
1answer
106 views

Trajectory of a projectile in a three dimensional space [closed]

$g$: the gravitational acceleration—usually taken to be $9.81\:\mathrm{m/s^2}$ near the Earth's surface $θ$: the angle at which the projectile is launched $v$: the speed at which the projectile is ...
0
votes
0answers
29 views

What is the temperature change for the adiabatic compression of $^3$He?

Given a phase diagram of $^3$He, consider the adiabatic compression of liquid $^3$He until it becomes solid. If the temperature of the fluid is 0.1 K (where dP/dT < 0), will the temperature after ...
3
votes
2answers
289 views

Will high amplitude, low frequency light be capable of wrapping around a macroscopic object? [duplicate]

To me, as a macroscopic observer of light, it appears that light moves in straight lines. If I shine a light at object A and object B moves between me and object A, the light hits, i.e. gets blocked ...
0
votes
2answers
61 views

Early simple electric generators

Can someone explain to me why it is B? Is it because eddy currents are induced on the side of the disk, and since it is connected to Y it basically goes through Y to X etc? But it is also connected ...
0
votes
0answers
40 views

Acceleration in AdS

I've been reading some notes ("Anti-de Sitter space" by Bengtsson) on anti-de Sitter space. It is shown in equation 152 that timelike observers at fixed radial distance from the origin experience a ...
1
vote
2answers
111 views

Can a glider maintain a constant forward velocity component?

I have a puzzle which asks me to consider a (engineless) glider descending at a constant rate and flying at a constant forward velocity (in still air). The question asks how to derive sink rate, $v_s ...
0
votes
2answers
111 views

Tensor product postulate [duplicate]

Non relativistic quantum mechanics assumes that a composite system should be described with the tensor product of the component systems. This is the tensor product postulate of quantum mechanics. I ...
1
vote
1answer
271 views

Two bodies connected by a spring

I came across of a problem. It is about two bodies with equal masses connected by a spring with the coefficient $k$ and the length of $l_0$. Suddenly, a constant force $F$ is applied to the first ...
1
vote
1answer
86 views

Bohmian trajectories vs. Feynman path integrals, continuous paths?

After reading some of the other posts online, I'm clear on the fact that Bohmian trajectories (of the de Broglie Bohm formulation) and the paths of the Feynman path integral formulation are very ...
7
votes
1answer
89 views

To what extent can one recover plane waves from the Airy eigenfunctions of a linear potential as the field is turned off?

Consider a single massive particle in one dimension under the action of a static linear potential, with the hamiltonian $$ \hat H=\frac{\hat p^2}{2}+\hat{x}F_0. $$ The eigenstate at energy $E$ is, ...
0
votes
1answer
60 views

Attenuation and Amplification - Transatlantic telecommunications cable system

It's a german book so I don't know if I'm translating this properly into english, so bear with me: The TAT-14 connects the cities Norden and Tuckerton with glass fibers (~7500 km). The cable has ...
0
votes
1answer
28 views

Can different energies be merged to “create” new kinds of energy, with respect to mass and energy conservations?

If energy and mass are the same thing, and matter which has mass -- chemicals to be exact -- can be combined to make new chemical compounds, can the same be done to energy? If so, how would it be ...
0
votes
1answer
31 views

Powering electromagnets with a piezoelectric charge

Could you power an electromagnet with the charge from a piezoelectric crystal like quartz and if you could would it be able to generate a strong magnetic field
0
votes
1answer
45 views

Why is $k$ left out of the equation $C_\text{all} = (k\epsilon_0A_1/d) + (\epsilon_0A_2/d)$?

The capacitance of two capacitors in parallel is found using this formula: $$C_{all}=C_1+C_2 \, .$$ Capacitance is $$C=\frac{Q}{V} \, ,$$ and also $$C=\frac{kε_0A}{d} \, ,$$ so can I say ...
1
vote
0answers
30 views

Polarizing cavity dumped laser light

From what I have read, most lasers are polarized because of Brewster windows. However, cavity dumped laser light never interacts with Brewster windows. Now, I know that there have been many cases of ...
0
votes
0answers
19 views

Magnetic harvesting

(I asked a question earlyer and then I realized that I had worded it in the wrong way so I am going to try again) so I was wonder if it was possible to harvest the magnetic energy from a permanent ...
0
votes
0answers
40 views

Nuclear Fusion using magnetic fields

I was wondering if you could use a very strong magnetic field to produce nuclear fusion. The basic idea is a spherical cavity containing Deuterium (and possibly tritium) nuclei whose walls will be ...
1
vote
0answers
46 views

Band-gap for solids with isoelectronic atoms

Isoelecronic atoms have same number of electrons but different nuclear charge. It is said that many of the chemical properties of these elements are equal or at least similar. Can I form solids with ...
1
vote
0answers
38 views

Supersymmetry breaking and normalizable zero modes

Why does supersymmetry always lead to normalizable zero modes? For example, it is stated in the paper by Michelson and Kaplan (http://arxiv.org/abs/hep-th/9510053) that we can assume, without loss of ...
1
vote
1answer
36 views

Behaviour of action with respect to time

I was wondering if it was possible to say something general on the behaviour of the action : $$ S[x(\tau)]=\int_0^T L(x,\frac{dx}{d\tau},t) dt $$ (where $x(\tau)$ defines a trajectory, with certain ...
1
vote
1answer
48 views

Coherent Polarization Beam Combination

All the papers I have read regarding coherent polarization beam combination split laser beams and then coherently combine the components. But is it possible to coherently combine two different lasers ...
0
votes
1answer
40 views

Are the edges of a galaxy moving inwards?

Space is expanding, but as I understand it, galaxies are not since gravity keeps them together. If you think of space becoming bigger, your galaxies just become further apart. But taking the size of ...
1
vote
1answer
219 views

Derivation of one-form/vector equation in Carroll confusion

I don't understand the derivation of Equation 2.14$$\mathrm{d}f\left(\frac{d}{d\lambda}\right)=\frac{df}{d\lambda} \tag{2.14}$$ in Carroll's Lecture Notes on General Relativity ...
10
votes
2answers
437 views

Is there any theorem that suggests that QM+SR has to be an operator theory?

UPDATE To make my question more precise, I'll define what I mean by an operator theory: An operator theory is a theory in which the dynamical objects are operators, i.e., the equations of motion ...
1
vote
1answer
134 views

Pascal's law in Fluid mechanics

Can we apply pascals law for accelerating fluids? If, yes then why. In a hydraulic lift, when pressure is applied at one end, the liquid in the tube accelerates so how can Pascal's law still valid?
0
votes
3answers
369 views

Acceleration of body rolling down inclined plane

Acceleration of a body rolling down an inclined plane is given by: $$\frac{g\sin\theta}{1+\frac{k^2}{r^2}}$$ $g$=acceleration due to gravity $\theta$=angle of inclined plane $k$=radius of gyration ...
0
votes
0answers
40 views

EM wave frequency and photon energy

We know that a quanta of light of frequency f has energy hf. But when I consider a single photon there is no concept of "frequency of a wave" because there is no EM wave associated with it which ...
-1
votes
1answer
60 views

Why is the expansion of universe continuously increasing? [closed]

If our universe is expanding and the concept of the multiverse is true, then why is the rate of the expansion of the universe increasing? Surely it must decrease?
-2
votes
1answer
36 views

Statics of a rigid solid [closed]

I need help with this problem... I need to calculate the angle so that this whole thing is in equilibrium. I don't have any problem with the conservation of the force. But when I get to the ...
0
votes
0answers
29 views

Calculate the parabollic trajectory

In order to calculate the parabollic trajectory (or ballistic) I need intrinsic equation. Now I need to integrate this equation but I don't know how. I would appreciate so much if you help me!

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