1
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0answers
5 views

What precisely does the 2nd law of thermo state, considering that entropy depends on how we define macrostate?

Boltzmann's definition of entropy is $\sigma = \log \Omega$, where $\Omega$ is the number of microstates consistent with a given macrostate. If I understand correctly, this means that it only makes ...
0
votes
0answers
12 views

What is angular speed after 2nd collision? speed of block? time? [on hold]

Question with graph: For a) I got that the mass for rod must equal to block for the block to stop immediately after the collision (perfect velocity transfer) so the initial speed for rod after ...
1
vote
1answer
19 views

Is the moment of a force the same about any point?

I know that when a body is is equilibrium There is zero resultant force in any direction, i.e. the sum of all the components of all the forces in any direction is zero The sum of the moments about ...
0
votes
0answers
14 views

Three level degenerate Hamiltonian with perturbation

I have the following system $$H=\begin{pmatrix}0&0&0\\0&0&0\\0&0&E\end{pmatrix}$$ $$V=\begin{pmatrix}0&0&\alpha^*\\0&0&\alpha^*\\\alpha&\alpha&0 ...
0
votes
0answers
3 views

Electrons Orbiting Sphere Magnet in Crooke's Tube

Were I to assemble a Crooke's Tube and insert a spherical magnet, with the poles of the magnet perpendicular to the electron stream, would the electrons begin to orbit the poles of the magnet as in ...
1
vote
0answers
12 views

Time Dependent perturbation driven at resonance

SO I am looking at driven perturbations, and I came across Fermi's golden rule here. It has a term that goes as: $$P\propto\frac{1}{\omega_{fl}-\omega}$$ Now I am curious how to go about solving this ...
0
votes
1answer
17 views

Height and pressure in atmosphere

Assuming an atmosphere will obey the hydrostatic equation dP/dz = -pg and the ideal gas law P = (p/uM)kT where M is the mass of a hydrogen atom, u is the mean molecular weight of the atmosphere, p is ...
1
vote
0answers
14 views

Has this boundary condition been used in fluid flow?

I would like to know whether anyone has seen a boundary condition used in a fluid flow problem, of the following type. Suppose viscous incompressible fluid is to the left of a plane $x_1=a$, so the ...
-4
votes
0answers
15 views

Electromagnetic induction problems [on hold]

1 What will happen to the illumination of the lamp (increase/decrease/remains constant) when decreasing the resistance R. 2 In the given figure a long wire is carrying a current of 5A, what is the ...
-4
votes
0answers
11 views

Electric current problems [on hold]

1 Calculate the equivalent resistance Ans: 8/3 Ω 2 Calculate the equivalent resistance Ans: 5Ω I've posted the answers for these problems to prove that this isn't some sort of homework,all i ...
0
votes
0answers
12 views

Powered Aquarium Siphon

I have an idea for a simple aquarium fill/drain construct made of PVC. Here is a basic diagram of my idea. When it is filling the fill valve, which is attached to a kitchen sink, is open and the ...
0
votes
0answers
13 views

Classical Scattering of Slow Neutrons by a Diatomic Molecule [on hold]

Consider an experiment in which slow neutrons of momentum $\hbar k$ are scattered by a diatomic molecule; suppose that the molecule is aligned along the $y$ axis with one atom at $y=-b$ and the ...
0
votes
1answer
19 views

Calculating kWh from time series of kW

I have a time series of kW where each sample is measured at regular intervals (10 seconds). Could anyone explain to me how could I calculate the total power consumed (kWh) over an hour? Thanks
0
votes
1answer
13 views

Why the crest of water absorb more light than the trough of water?

I have done my experiment using water ripple to study the behavior of waves. I know that the crest will absorb more light than the trough so that the image created on the white paper sheet appeared to ...
0
votes
0answers
14 views

Relationship between the fall time and projected area

I am investigating the relationship between the fall time of a paper tray and its projected area. In this investigation I have been using the following variables: Controlled Variable: The air ...
-3
votes
0answers
23 views

Quantization of linear momentum in 'particle in a box' problem

I am new in Quantum Mechanics. I am 2nd year UG (Physics Major). I had few conceptions to clear.. I was going through particle in a box problem ...So while deriving that we used the time independent ...
6
votes
1answer
43 views

Why do clouds fly?

I know it's probably the most stupid question there is, but why do they fly are the clouds lighter than air? What's keeping those tiny ice structures floating miles about the ground? I've been looking ...
2
votes
1answer
27 views

What is meant by incompressible flow?

What is meant by incompressible flow? The density of the fluid is a constant, $\rho = constant$ The density of a fluid has a spatial dependence but remains constant in time, $\rho = ...
1
vote
1answer
25 views

Probability distribution in phase space and Liouville's theorem?

We can define a probability distribution over phase space (say 1D) $\rho(x,p)$ such that, for example, $$\langle x\rangle = \int \rho(x,p) dxdp$$ etc. It can be shown here that such a distribution ...
1
vote
0answers
27 views

Who was the R. Dolen behind Dolen-Horn-Schmid duality? [on hold]

Can you provide biographical information for R. Dolen, known for Dolen-Horn-Schmid duality?
1
vote
1answer
72 views

Why isn't the $\lvert\phi(x)=0\rangle$ Fock eigenstate the vacuum state?

If, in a QFT of a scalar field $\phi$, a Fock space $n$-particle position eigenstate $\lvert x_1\cdots x_n\rangle $ is given by $$ \lvert x_1\cdots x_n\rangle ...
1
vote
0answers
19 views

Show the Lie algebra is the same for $SU(2) \times SU(2)$ and Lorentz group

So I know: $$[\sigma_{I},\sigma{j}] = 2i \epsilon_{ijk} \sigma_{k}$$ So two products of this should give us the Lorentz group: $SO(4) = SU(2) \times SU(2)$ Where $SO(4)$ has 3 Lie algebra which can ...
1
vote
0answers
7 views

What is clock or phase adjustment in projectors? Why its proper setting eliminates strange behaviour of 1px lines/

I'm doing experiments that require using a big, thin, contrast grid, for example 1 black pixel and then 1 white pixel alternately. I've met with a few DLP projectors and in each of them I had to ...
-1
votes
0answers
16 views

what will happen when you attached your hand to a two 220 volt wire of their phase defference by 120 degree?

What will happen when you attached your hand to a two 220volt wire with their phase difference by 120 degree?
-2
votes
0answers
67 views

Is this picture of the universe valid?

Universe as a whole has zero entropy. Since entropy does not grow, the universe has no time arrow. It does not change over time, at best it only fluctuates. Since following Holographic principle the ...
0
votes
1answer
19 views

First Order Time Depenent Perturbation theory of particle in magnetic field

So I am dealing with the following hamiltonian, and the following perturbation: $$H=-\mu B_0\sigma_z$$ $$V=\mu B_1(\cos(\omega t)\hat x-\sin(\omega t)\hat y)\cdot{\bf \sigma}$$ I am asked for the ...
1
vote
0answers
27 views

What is the Electric field of an infinite line charge while on the same axis

Consider a line of charge (w/ charge per unit length lambda(L)) which extends along the x-axis from $x = -\infty$ to $x = 0$. (a) Find the electric field at any point along the positive x-axis (b) ...
0
votes
0answers
14 views

Spin connection in higher dimension

I have a problem regarding computation of spin connection in the case where One or more dimension is comactified. For example if we take a $D+1$ dimensional bosonic string action and write the D+1 ...
0
votes
0answers
11 views

Solving relativistic particle decay problem in Landau

In Landau, Lifshitz "The Classical Theory Of Fields" in $\S11$ "Decay of particles" a problem is given: A particle moving with velocity $V$ dissociates "in flight" into two particles. Determine ...
0
votes
1answer
24 views

What happens to an Electron when its charge is transferred elsewhere

I am vastly uneducated in the areas of physics and chemistry. I am aware that electrons do have a mass, and that they carry a charge. I think that when an electron gains energy it becomes excited and ...
0
votes
3answers
51 views

Why don't the kinematic equations agree with calculating velocity one second at a time?

A car is moving at a velocity of $10 \, \text{m}/\text{s}$. After point $A$ no acceleration is provided. By simple measurement, the acceleration is found to be $-1 \, \text{m}/\text{s}^2$. Using ...
1
vote
0answers
27 views

Sum of forces with liquid in rotation

I would like to compute sum of forces on this study (water pass between green/blue walls): A blue container has water inside. A green volume has nothing in it, I consider mass like 0. I know force ...
0
votes
1answer
30 views

Distance travelled given velocity at various moments of time

I am trying to solve a problem where I need to find the distance travelled at the end of the nth second and my input data contains only velocities at different time instances. Say for instance I ...
6
votes
0answers
41 views

A graphical proof that the $SU(2)/\mathbb{Z}_2$ vortex is non-orientable

The text, see [1], compares the vortex solutions of a spontaneously broken symmetry $U(1) \rightarrow 1$ and $SU(2)\rightarrow U(1) \rightarrow \mathbb{Z}_2$. The vortices can be classified by ...
1
vote
1answer
22 views

Why are there interference patterns inside a diffraction envelope?

When double-slit diffraction occurs, there are interference patterns inside, say, the central diffraction maxima (or envelope). I am trying to understand how these interference fringes are created. ...
1
vote
1answer
14 views

Why maximum energy transfer at natural frequency even if max amplitude occurs below $f_0$

This is a paragraph from my book: "For a damped system, the resonant frequency at which the amplitude is a maximum is lower than the natural frequency.However, maximum transfer of energy, or energy ...
1
vote
1answer
20 views

Two-Body with external force - energy confusion

Setup Imagine a two-body system of masses under a classical mechanics model. The separation and mass-ratio doesn't matter for this example. Presume they are initially stationary. Now suppose that we ...
0
votes
0answers
19 views

How do RGB colors work? [duplicate]

They say that all colors can be formed by mixing Red, Green, and Blue appropriately. Is it true? Isn't the Fourier basis infinite dimensional? Or does it turn out to be the case that only three ...
0
votes
3answers
55 views

why exactly is ice less dense then water?

The answers to this question explain that ice is less dense than water because it has a "crystal structure", but they dont explain what exactly that is and why this happens, also I saw this answer ...
3
votes
1answer
39 views

Why are neutrino and antineutrino cross sections different?

Particularly in the case of Majorana neutrinos, it seems a little odd that the particle and antiparticle would have differing cross sections. Perhaps the answer is in here, but I've missed it: ...
3
votes
2answers
241 views

Virtual particles and physical laws

Recently, I was reading about Hawking Radiation in A Brief History of Time. It says that at no point can all the fields be zero and so there's nothing like empty space(quantum fluctuation etc.). Now, ...
1
vote
0answers
14 views

How do I describe two entangled electrons in the same state except for a different spin

I am trying to formulate the wave function that describes two entangled electons having the same position but opposite spin. According to the Pauli exclusion principle this should be possible. And ...
0
votes
1answer
15 views

Capacitance of a parallel plate capacitor with joint plates

What is the capacitance of a parallel plate capacitor with plates joint with a thin metal strip diagonally like this |\| I am confused. Is it infinte or 0.
0
votes
1answer
31 views

Coriolis Force in a Merry go Round

Suppose there is a person standing in a Merry go Round, which is rotating at a constant angular velocity $\vec \omega$. He experiences, of course, a centripetal acceleration $\vec a_{cen}$ and has ...
1
vote
0answers
20 views

Causal Green Function in D=2 for D'Alembertian

I'm trying to obtain the Causal Green Function for the D'Alembertian in D=2, I'm finding $$G^{(2)}_C (t; \vec x) = \frac{1}{4\pi} \frac{\Theta(t^2-\vec x^2)}{\sqrt{t^2-\vec x^2}} - \frac{i}{4\pi^2} ...
-3
votes
1answer
17 views

Work done from force-extension graph

The answer is C, but I got B... F at 3cm = 10, F at 6cm = 20 $W=F\cdot s$ $(20-10)\times 3=30$ I must have made a mistake or stupid assumption then, how am I meant to get 45 N cm?
1
vote
0answers
20 views

Gregory-Laflamme Instability

Certain solutions to the low energy effective action of string theory, namely black strings and branes, were shown to exhibit an instability via perturbation theory. Specifically, the metric is ...
-2
votes
0answers
17 views

Arrow of time and virtual reality [on hold]

As we know that in classical world we have a clear arrow of time which points towards future..We can see glass falling from table and break but not the opposite in our world and whole universe... If ...
0
votes
0answers
16 views

Wannier functions on a ring

Let's say I have a single particle hamiltonian in a periodic potential. For example a 1D lattice such that: $$H = -\frac{\partial_x^2}{2m} + V(x) $$ with $ V(x+a) = V(x)$ where $a$ is the lattice ...
1
vote
0answers
41 views

Link between a topological space and a manifold [migrated]

A topological space is defined as a non-empty set $X$ together with a given collection of subsets $T$ (topology) of $X$, such that, (i) any union of these subsets is one of the subsets. (ii) any ...

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