1
vote
1answer
11 views

Will the gravitational pull of air affect the falling rate of an object?

After looking at this question: Don't heavier objects actually fall faster because they exert their own gravity? A thought occurred to me that due to the increased gravitational pull of the ...
0
votes
0answers
8 views

Aplications of algebraic topology/pure mathematics in nuclear fusion

I am planning on working on an independent research class this fall at a community college. My instructor wants to focus it around pure mathematics/topology/homotopy. I think she has done a phd in ...
0
votes
1answer
12 views

How does gravitational time dilation work in artificial gravity made by rotating a cylinder?

Concerning gravitational time dilation in artificial gravity (made by a rotating torus like in many sci-fi movies) how would you go about calculating the effect?
-1
votes
0answers
16 views

Intro Mechanics: Finding ball speeds after collision

So I'm reading about conservation of energy, momentum, balls colliding etc. and unsurprisingly there are hundreds of questions in my textbook where essentially they give me some of the variables (m1, ...
-1
votes
0answers
5 views

Electrical resistivity: the effect of adding electrons

Consider a copper wire of fixed length and cross-sectional area, and apply an electric field to the wire induced by a fixed potential difference $V$ across the two endpoints of the wire. The intensity ...
0
votes
0answers
16 views

Gedanken experiment: Does it collapse to a black hole or not?

Imagine that I am a stationary far-off observer of a massive star that is minutely larger than its Schwarzschild radius (in other words, its on the verge of collapsing). My spacecraft accelerates ...
0
votes
1answer
26 views

Minima & maxima of Laplace's equation

I don't get the following sentence from David J. Griffiths' Introduction to Electrodynamics (the ambiguous sentence is in bold) Laplace's equation tolerates no local maxima or minima; extreme ...
0
votes
0answers
33 views

In how lmuch time will the year be exactly 365 days? [on hold]

I understand that the number of days per year has changed throughout the history of the Earth. Apparently there were once over 400 days per trip around the sun. How long will it take approximately ...
-1
votes
0answers
14 views

Books of dynamo theory

I wanted recommendations of dynamo theory pdfs to make a report about magnetic fields of planets and stars with all the math behind it, like vector calculus, Lagrange functions, partial differential ...
0
votes
2answers
59 views

Faster than speed of light [duplicate]

I was watching a Physics TV show, When someone called Alex Filippenko said that when there was the Big Bang, the Space extended at a speed faster than speed of light. He said that it wasn't against ...
0
votes
1answer
13 views

Number of classical oscillation modes of a Lattice and number of quantum phonons

In solving the Classical model for lattice dynamics [Rossler pag 38] we find that the lattice admits $$d\cdot N\cdot r = \#modes$$ where $d=$dimension of the problem $N=$ number of atoms $r=$ ...
0
votes
1answer
42 views

Isn't the aether existant

Before you say I'm wrong consider this, Einstein is supposively the first person to get completely get rid of the various aether models that were proposed. But didn't Einstein actually prove them ...
0
votes
2answers
26 views

How are standing waves a result of constructive and destructive interferences?

For constructive I can understand. But destructive I can't. I can not picture the shape of two pulses or waves maybe that form the resulting standing wave. The places where waves are canceled just ...
0
votes
0answers
20 views

how to calculate force needed to launch an object of known mass vertically?

I am going to contract a spring and release it to project an object of known mass to a specified distance upwards(vertically).I want to calculate the needed force to overcome gravity and reach the ...
-1
votes
2answers
45 views

Would a person gain or lose weight after expelling a flatus?

Considering the chemical composition, mass, and pressure range of typical human flatulence, would a person gain or lose weight after passing gas?
0
votes
0answers
10 views

Detrended Fluctuation Analysis

In the fitting procedure of DFA, how can we understand which order of DFA (Detrended Fluctuation Analysis) (DFA1, DFA2, and higher order DFA) should be applied in the time series?
0
votes
0answers
16 views

What determines a particles probability of creation?

I know when we're discussing events at a quantum level, we deal in probability and not absolutes. What I'm looking to understand, is when articles I've read on particle physics state a particle has a ...
-1
votes
0answers
31 views

How do I calculate momentum for a particle in a box, using the momentum quantum operator?

For a particle in a one dimensional box with $U(x) = 0$ between $x = 0$ and $x = L$ (infinite Potential well) the momentum for $n = 1,2,3,...$ is given by: $$p_n = \frac{nh}{2 L}$$ The wave ...
1
vote
0answers
21 views

Variation of quadratic term in modified Einstein-Hilbert actions

In the context of mimetic gravity at some point one try to add to an already modified Einstein-Hilbert action also a term like $$ S_\chi=\int\,d^4x\,\sqrt{-g}\frac{1}{2}\gamma\chi^2,\qquad(\star) $$ ...
0
votes
0answers
24 views

Plane wave solutions of Dirac equation

I'm reading chapter 3 in Peskin on the Dirac equation. First of all, they say since Dirac satisfies Klein Gordon it can be written as a linear combination of plane waves. This is fine. So a general ...
2
votes
1answer
31 views

Are there any other pairs similar to virtual and normal photons?

Are there virtual particles for every kind of particle there is?
0
votes
2answers
42 views

Atoms In Space - More Specifically Helium [duplicate]

I've read several articles regarding the limited supply of helium gas on our planet and one that many scientists/engineers require for their research. I suppose if the government were to issue any ...
0
votes
1answer
25 views

Slingshot Energy into traveled distance [on hold]

If I have a slingshot and I am told that when pulled it has about $E$ joules of energy, how do I compute the height at which an object of mass $m$ would travel if the slingshot is released in the ...
1
vote
3answers
42 views

Why spinning a pen makes it easier to remove it from the stand?

I have a ballpoint pen stand on my desk. The pens are held inside their caps with the point down, like this one (but not as fancy): If I try to simply pull up one pen, the friction between cap and ...
1
vote
1answer
27 views

The GHZ-State in conflict with local realism

Consider three, with respect to their polarisation, entangled particles in the following state: $|\psi\rangle = \frac{1}{\sqrt2}(|H\rangle_1|H\rangle_2|H\rangle_3 + ...
0
votes
4answers
47 views

Why does a current-carrying conductor behave like a magnet?

I have heard that a current-carrying conductor behaves like a magnet, the reason why the magnetic needle of a compass kept near the circuit, deflects. Why is it so?
-3
votes
1answer
31 views

Question to find distance at which 2 trains will pass each other [on hold]

I was solving some questions related to motion, and I came through a question which I cant understand. The question goes like this: Two trains A and B, 100 km apart are approaching towards each ...
2
votes
2answers
28 views

Is sonic boom louder than the sounds that a object traveling at the speed of sound makes, if so why?

Here are the wave-front models for both: I am in an introductory physics course. Just learned about this. I am not entirely sure if sonic boom is louder. But from what I saw, it's loudness is ...
2
votes
3answers
49 views

How does a converging-diverging nozzle not violate conservation of energy?

Disclaimer: I know absolutely nothing about fluid dynamics, and very little about physics in general. THis may be a really dumb question. Now, at subsonic speeds, converging and diverging nozzles ...
0
votes
0answers
25 views

Fixing time in Feynman phase space path integral

The phase space version of Feynman's path integral expression for the free particle propagator involves a (formal) sum over paths in phase space with fixed $q$ endpoints and (as far as I'm aware) ...
2
votes
3answers
102 views

Why does time evolution operator have the form $U(t) = e^{-itH}$?

Let's denote by $|\psi(t)\rangle$ some wavefunction at time $t$. Then let's define the time evolution operator $U(t_1,t_2)$ through $$ U(t_2,t_1) |\psi(t_1)\rangle = |\psi(t_2)\rangle \tag{1}$$ and ...
1
vote
3answers
61 views

Why do telescopes move synchronously?

Here's a very nice video (see it in HD) of timelapses captured at the atacama desert. In the beginning of the video you can see that 4 telescopes move synchronously. Could anyone explain why? I always ...
2
votes
1answer
34 views

What is a single-phonon?

From what I understood from wikipedia, as well as some other resources, each phonon corresponds to a normal mode oscillation, and the creation operator to create a phonon of wavevector $k$ is: $$ ...
1
vote
1answer
27 views

Archimedes Principle

Say I have an arbitrary body $\Omega$ and surface $\partial \Omega$ submerged in a hydrostatic fluid of density $\rho$ under the influence of gravity. How does one show Archimedes Principle? i.e. ...
2
votes
1answer
30 views

Can the magnetic force between two magnets be explained classically via magnetization current?

Usually in Electrodynamics courses the magnetic forces are analysed via wire-wire interaction. I don't remember being shown a classical explanation for magnetic forces between magnets. Since it is a ...
3
votes
1answer
39 views

Mechanism for inelastic collisions in the particle world

We know that inside particle accelerators we collide ionized particles. But we also know that in the microworld all collisions are elastic (due only to the electrostatic force?) between the particles. ...
-6
votes
0answers
28 views

Particle Physics [on hold]

Which of these statements are true? A. temperature becomes very high during this process. B. pressure becomes very high in this process C. fission fragments are radioactive D. alpha-rays are ...
2
votes
1answer
35 views

Why do the two amplitudes need to match together through the region between the boxes?

This is an excerpt from Feynman's lectures 3; Suppose we think of the situation in Fig. 7–3, which has two boxes held at the constant potentials $ϕ_1$ and $ϕ_2$ and a region in between where ...
-2
votes
0answers
11 views

Critical angle and Apex angle of prism [on hold]

I was studying geometrical optics particularly refraction on a prism and thougt that if we change the apex angle of prism by some means or if we take different prism with different apex angle , will ...
0
votes
1answer
27 views

The Riemannian Curvature in Deformations

Is there a direct correlation between the Riemannian Curvature tensor and the deformation gradient tensor in continuum mechanics?
2
votes
1answer
38 views

Reflection of an Electron

When a mechanical wave goes from one material to an other, some fraction of it returns back. Same thing with light (massless), but what happens with an electron? When the "wave function" changes ...
0
votes
0answers
31 views

Do the eigenstates of the Pauli operators correspond to the six directions of the 3D world?

I understand that the six eigenstates of the three Pauli operators $X, Y, Z$ correspond to the six poles of the Bloch sphere. By fixing an orthonormal basis of our physical word, does "measuring Pauli ...
1
vote
1answer
18 views

Obtaining central force from the potential of an off-orgin object

I was trying to go through a simple exercise and was getting tripped up on the mathematical intuition of my elementary physics. I thought I should be able to get any old central force from the central ...
-1
votes
0answers
37 views

Proof of Poisson equation in a gravitational field [on hold]

Can anybody show me how to prove Poisson's equation in Newtonian Gravitational field?
-1
votes
2answers
39 views

Why is the index of refraction different for different wavelengths? [duplicate]

The index of refraction can be written as $$n=\frac{\lambda_v}{\lambda_m}$$ where $\lambda_v$ is the wavelength in a vacuum and $\lambda_m$ is the wavelength in the medium. I’ve been told that since ...
2
votes
2answers
29 views

Many cells in parallel

If two or more cells of unequal voltages are connected in parallel (with the same terminal on the same side), is there a formula that gives the net potential difference? Also, by Kirchoff's loop law, ...
1
vote
1answer
37 views

How can we account for a friction force changing sign in a conservation of energy equation?

I want to solve a simple mechanical problem whereby three forces act upon an object. $F_1 = (10 - x)$ N $F_2 = -3 N$ (friction force) $F_3 = -10x$ N So at $x$ = 0 we see that $F_1$ + $F_2$ + $F_3$ ...
-2
votes
0answers
17 views

effective mass in a Bohr atom

I was solving a question in a hypothetical situation, in which a carbon atom consists of 6 pions instead of an electrons. Acoording to bohr model of an atom,what would be the ground state energy of ...
1
vote
1answer
27 views

When is the phase space diagram an ellipse?

For a two dimensional dynamical system, when does the phase space diagram give an ellipse? I know about the examples for damped and undamped harmonic oscillators, but our instructor said that the ...
1
vote
0answers
18 views

How do I calculate the maximum pressure a container can withhold?

Say I have a spherical container with a certain gas inside, heated to a very high temperature, and thus a very high pressure. The gas will exert a force radially outwards onto the container, and at ...

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