All Questions

63 views

How can current be a smooth curve?

The following is a graph of the current across some circuit element: Note how the current is treated like a smooth continuous function. Even in the analysis of things (i.e. analysis of the ...
81 views

Why does Gauss's law work for a charge off center in a spherical surface?

CASE 1: Consider an enclosed spherical surface with a charge $q$ at its centre. From Gauss' law we can say that the flux through this sphere is $q/\epsilon_0$. CASE 2: The charge is inside but off ...
48 views

From a cross section to a probability

This is homework problem: Given the cross-section of a neutrino-electron scattering, what is the probability for a solar neutrino to scatter with a electron as it goes through the center of the Earth? ...
65 views

Quantum Mechanics - Observable

If $O$ represents an operator corresponding to an observable why does the following equality hold? $$\langle f(x)\, |\, O g(x)\rangle = \langle g(x) \,|\, O f(x) \rangle$$ It is used on the last ...
28 views

Approximation of skeleton diagrams

I'm studying the diagrammatics for a Bose system (in the superfluid phase) developed by Gavoret and Nozieres (Annals of Physics 28 349 (1964)). In this paper, they show how to solve the problem using ...
17 views

If two objects collide, will the collision force be twice as big as the original force? [duplicate]

Say, if we have two trucks travelling towards eachother at 60m/s, and those two trucks carry the same payload, and are the same model (aka they're exactly the same), will the collision force be as if ...
45 views

'Warp'- type travel; is it possible?

I just re-read an article about space travel, and the same article claimed that Star Trek-type 'warp' nuclear engines ARE theoretically possible, but that it will take around 500 years for humans to ...
56 views

Inertia matrix of a rod rotating about an axis [on hold]

I'll provide a picture for clearer understanding. The problem is to calculate the angular momentum of the rod rotating about the z-axis. I have serious difficulties in deriving the inertia matrix, ...
33 views

group and phase velocity of free particle [duplicate]

If Schrödinger wave equation is for matter waves then for a free particle Group velocity $V_g =2$ Phase velocity $V_p$ But matter waves satisfy the relation $V_g V_p = C^2$ where $V_p>C$ Does this ...
36 views

Franck and Hertz graph function

I need a function whom graph is the following (the Frank and Hertz experiment graph): Currently I wrote the following function: ...
46 views

Is there just one fundamental frequency?

I read simple definitions of the terms frequency, and fundamental frequency, which defined them thus, Frequency: the number of occurrences of a periodic wave during a second Fundamental Frequency: ...
42 views

Chemical potential of Bose-Einstein condensation

This is a problem in An Introduction to Thermal Physics. (a)(b) is easy to work out. In (c), I use the formula $N_{excited}=(\frac{T}{T_c})^{3/2}N, \ (T<T_c)$ to calculate how many atoms are ...
31 views

Thermodynamic Processes [on hold]

can someone help me in these problems? -An isentropic process occurs at a constant entropy,what is a "entropy"?(what mean)? -An isenthalpic process introduces no change in enthalpy in the ...
40 views

Rigid rectangle in Schwarzschild

Say I build a perfect rectangle. Side lengths $l_1$ and $l_2$ and perfect right angles. I am on earth and the metric is given by the Schwarzschild metric. Setting $dt=0$ leads to the spatial ...
51 views

Difference Between Algebra of Infinitesimal Conformal Transformations & Conformal Algebra

in Blumenhagen Book on conformal field theory, It is mentioned that the algebra of infinitesimal conformal transformation is different from the conformal algebra and on page 11, conformal algebra is ...
206 views

How does the frequency of a particle manifest itself?

In terms of wave-particle duality for, let's say a photon; how would the frequency practically manifest/demonstrate itself? Like, i understand that the frequency is related to the energy a particle ...
3k views

Was Titanic's captain's decision correct?

I just saw a documentary on Titanic. Someone in that documentary told Captain Smith "Shall we close the water tight doors, sir?" and the Captain replied "No, let it be open. Let the water ...
35 views

Doppler spectroscopy to verify Earth's speed around the sun

I'm looking for data points to check changes in $z$ as the Earth moves towards and away from a star. I'm finding lots of data for various objects [1] but lots of variation too (for eg, the results for ...
40 views

Reason for the experiment [on hold]

Why is the independent confirmation by separate experiments such as important part of the development of the idea of the existence of electron wave?
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Separation of radio frequency [on hold]

In driving due north along straight road driver notices that the radio station she is listening gets louder and quieter as she drives along. Explain this, if she can see two separate radio ...
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I have read that adiabatic process is isentropic because there is no heat exchange in an adiabatic process and thus no change in entropy. But my question is - Even in adiabatic process, work can be ...
35 views

How to calculate the gravity level at the boundaries of a black hole? [on hold]

Imagine that a body is attracted to a black hole and it has a mass $M$, if the body is moving with $v=.99c$, will its speed and mass affect the gravity relation between the body and the black hole? or ...
208 views

Position dependent speed, how to compute position

I can't solve a problem: $A= 0.5 (ms)^{-1}$, $x_0 = 0.5 m$, $v(t)= A \cdot x^2$, I have to compute the position at $t=3$ ($x_0$ is the initial position). So my guess is that I should be able ...
15 views

Generate unit cell from space group

I am trying to make a code to generate primitive unit cell. I have the space group and coordinate of inequivalent sites and lattice parameters. I want to generate the primitive unit cell from that. ...
10 views

Solving oscillation-related problems using energy [on hold]

I am very much interested in how exactly can one solve harmonic oscillation-problems using solely the KE - PE approach. I am a high-school student, so a little in-depth explanation will very much be ...
35 views

Boundary conditions for the heat equation when solving a mass density gradient

I'm working with a mass density gradient with length $L$ and I'm trying to solve the heat equation in 1-D (mass diffusion equation, $\partial_t\rho(t,x)=D\Delta\rho(t,x)$), but I'm not sure which ...
70 views

Looking for the name of a physical phenomenon in fluids' mechanics

I have not even an idea about how I would search for that on Google, that is why I'm trying my chance here. As electrical engineer I have no clue about fluid mechanics. We all now that when water is ...
39 views

I read about the Michelson-Morley experiment (forgive spelling) showing Ether as an unnecessary concept for what might have been a medium for light waves. What if space-time is 'saturated' with so ...
25 views

Band structure and band index

Please let me know If my understanding is right. For a given $\vec{k}$, $H$ is a function of $\vec{k}$ the energies vary discretely for $n$ ie.,the band index. For a given $n$, we choose all the ...
27 views

Density of States of Free Particle in One Dimensions

I am using Quantum Mechanics by David H. McIntyre, chapter. This is problem 15.7: Find the density of states $g(E)$ for the case of a free particle in one dimension; further, show that the density of ...
36 views

Angular momentum Bohr's model

I have been trying to derive speed, radius etc. in hydrogen atom using Bohr's postulates and not neglecting the coulombic attraction on proton. I know that they will be revolving around their centre ...