1
vote
1answer
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 ...
1
vote
1answer
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 ...
1
vote
1answer
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? ...
0
votes
1answer
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 ...
1
vote
0answers
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 ...
0
votes
0answers
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 ...
-3
votes
2answers
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 ...
0
votes
2answers
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, ...
0
votes
0answers
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 ...
1
vote
1answer
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: ...
1
vote
2answers
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: ...
0
votes
1answer
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 ...
-2
votes
0answers
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 ...
3
votes
0answers
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 ...
3
votes
1answer
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 ...
5
votes
2answers
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 ...
22
votes
1answer
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 ...
1
vote
2answers
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 ...
0
votes
1answer
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?
-2
votes
1answer
23 views

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 ...
2
votes
1answer
9 views

Why is adiabatic process isentropic?

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 ...
-1
votes
1answer
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 ...
1
vote
2answers
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 ...
-2
votes
0answers
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. ...
-1
votes
0answers
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 ...
-1
votes
1answer
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 ...
-1
votes
1answer
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 ...
-2
votes
1answer
39 views

About light waves [on hold]

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 ...
-1
votes
1answer
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 ...
-1
votes
0answers
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 ...
-3
votes
1answer
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 ...
-1
votes
0answers
15 views

A problem concerning the calculation of parameters in a periodic system [on hold]

I am using Quantum Mechanics by David H. McIntyre, chapter 15. The question is 15.8: Find the single bound state energy of an electron in an isolated well of depth $V_{0} = 1$ eV and with width $b = ...
-1
votes
2answers
58 views

The speed of light and unstable matter

Mr.E is on a luxury spaceship travelling about 1/2 the speed of light and finds a cubic lump of unstable matter(attached to a bomb) in his cabin. He of course is an expert with bombs but this device ...
2
votes
1answer
54 views

Does timbre consist in pitch and volume?

I read that the physical properties of a sound wave correspond to its audible qualities: pitch, volume, and timbre. However, an oscilloscope uses only two-dimensions to accurately depict the physical ...
-3
votes
1answer
44 views

How far in meters from the Sun's center is the Earth-Sun center of mass?

Like any set of massive objects separated by distance, the Earth and Sun have a center of mass. How far in meters from the Sun's center is the Earth-Sun center of mass? Just curious? Also what percent ...
2
votes
1answer
65 views

Statistical count

I am reading the book"Heat and Thermodynamics" by Mark Waldo Zemansky and Richard Dittman. In the chapter "Statistical Mechanics" it says if I have $N_{i}$ distinguishable particles in any of $g_{i}$ ...
0
votes
1answer
60 views

How are magnetic and electric fields transmitted?

This may be a duplicate, but how are (ideally) constant E- and B-/H-fields transmitted thru space? In this situation I like think of EM radiation as a note from a particle informing the universe of a ...
2
votes
2answers
92 views

Which solution to the electromagnetic wave equation is the most accurate model of monochromatic light?

When a photon is modeled as a monochromatic electromagnetic wave its electric and magnetic components are usually taken to be sine waves (for example here ...
5
votes
4answers
496 views

How are electric flux calculations not double integrals?

A disk of radius 0.10 m is oriented with its normal unit vector $\hat{n}$ at 30$^{\circ}$ to a uniform electric field $\vec{E}$ of magnitude 2000 N/C. What is the electric flux through the disk? ...
0
votes
1answer
67 views

Metric for infinite straight cosmic string

A string theory question on my general relativity problem set: Metric is given as $$\mathrm{d}s^2 = -A(r)\mathrm{d}t^2 + B(r)\mathrm{d}r^2 + r^2 \mathrm{d}\theta^2.$$ a) Solve the vacuum equations ...
2
votes
0answers
22 views

How do I determine resistivity from electron defects of high purity gold?

I am trying to create a plot for the electrical resistivity of high purity gold from 1 K to 1000 K. I found gold's resistivity at 300 K using the Wiedemann-Franz Law based on thermal conductivity data ...
0
votes
0answers
18 views

Lateral forces on earths surface

If a giant stone sphere was sitting on the earths surface, would it experience a later force due to the earths rotation? For example my intuition tells me that if there was a sphere a mile high ...
-2
votes
0answers
17 views

What are the New Researches in the field of laser physics? [on hold]

I want to know the newest updates of science in the laser physics researches specially the theoretical part of it.
1
vote
2answers
56 views

Protons and Electrons Occupying the Same Space

When it comes to atoms electrons can't fall into the nucleus, which besides the off hand uncertainty explanation, I'm not sure which force prevents them from falling into the nucleus. I thought I ...
2
votes
0answers
65 views

Is there any distinction between these products: scalar, dot, inner? [migrated]

I hope you will forgive a math question that comes up in physics contexts where language is loose. There is a product which can be defined on a vector space that takes two vectors and returns a ...
1
vote
4answers
82 views

Why can computer circuits recognise only two states? [on hold]

Computers can only understand binary (that is 0s or 1s). I want to know Is there any way that computers can understand more than 2 states. I know that It is much harder to build components that use ...
4
votes
0answers
27 views

R-symmetry commutator

I've seen the claim made several placed; Terning's "Modern Supersymmetry" p. 5 on N=1 SUSY algebra states it as well as anyone: The SUSY algebra is invariant under a multiplication of $Q_\alpha$ ...
5
votes
1answer
76 views

“Imaginary” Perfect Time

In the definition (in one spatial dimension) of $\Delta \tau$ there is the relation: $(\Delta \tau)^2 = (\Delta t)^2 - (\Delta x)^2$ which is invariant. If $(\Delta x)^2 > (\Delta t)^2$ then there ...
0
votes
0answers
38 views

Demonstrate identity $\int_{0}^{x} \int_{0}^{\xi}f(s)dsd\xi=\int_{0}^{x}(x-\xi)f(\xi)d\xi$ [on hold]

I have trouble doing the following problem, I have not been able to make even the first part, I was hoping someone could help me. The problem is: Show that: $$\int_{0}^{x} ...
10
votes
1answer
139 views

Can nowadays spin be described using path integrals?

In Feynmans book, "Quantum mechanics and Path Integrals" he writes in the conclusions (chapter 12-10) With regards to quantum mechanics, path integrals suffer most grievously from a serious ...

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