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9 views

About tension in spring

I have confusion related to tension in string. I know that spring force does not changes immediately.But what happened to tension T in string when we cut spring k1.Does it change or remain same.And ...
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0answers
6 views

Average speed and Average velocity

Suppose moving from my house to my school through a curved road,it takes suppose 30min and 30m then Average Speed=30m/30min Hence my average speed would be 1m/min then by taking the shortest path ...
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0answers
3 views

Two objects undergoing proper acceleration

Is there an inertial frame (x', t') in which two objects undergoing proper acceleration in the positive x-direction (e.g. starting from rest at t=0 from x=0 and x=L) where the two objects end up at ...
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2answers
11 views

Does action at distance in electromagnetism violate energy conservation?

Consider two charges A and B separated at distance D. charge B is attached on spring and can move towards and away from charge A. Now charge A is brought closer to charge B and then it is taken back ...
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16 views

Is the age of the universe 13.799±0.021 billion years OR 2.935364e+18 second(s)?

According to wikipedia (https://en.wikipedia.org/wiki/Observable_universe), The observable universe is thus a sphere with a diameter of about 28.5 gigaparsecs (93 billion light-years or 8.8×10^26 ...
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0answers
7 views

How does the $U(1)$ global symmetry break in the gauged $XY$ model?

I'm studying the particle vortex duality, and I'm confused how we're able to say that in the Coulomb phase, the "hidden" $U(1)$ global magnetic symmetry spontaneously breaks. gauged XY model: $\...
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0answers
13 views

Solution to object with proper acceleration

An object undergoing constant proper acceleration has the 4-vectors describing their location obey $$\frac{d\vec r }{d\tau }\cdot \frac{d\vec r}{d\tau }=-1$$, $$\frac{d^2\vec r}{d\tau ^2}\cdot \frac{d^...
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0answers
12 views

Are neutron star cores thought to be stiffer than photon gases?

The weak energy condition allows anything from -1 to 1. Cosmic inflation and dark energy are very close to the limit of -1. Both photon gases and ultra-relativistic degenerate gases are +1/3, but can ...
-4
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1answer
26 views

Dark matter - Graviton

Ok, I have been thinking of this for a long time. I have made a theory about the quantization of gravity and gravity more generally. Yes you heard me right. Please do not leave. This post is not a ...
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0answers
8 views

Quantum statistics of a particle in a magnetic field

Let us consider the statistical physics of a single particle (without spin) moving in a magnetic field described by a vector potential $\vec{A}$ at a finite temperature $1/\beta$ on a $2$-dimensional ...
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17 views

Is it possible to encode a message in such a way that can only be read by someone or something capable of seeing into the very near future?

Say you have some way of seeing somewhere between a microsecond to 0.1 seconds into the future, or at least the most likely future. Is it possible,through something like a flip-book effect or some ...
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0answers
3 views

What is responsible for large ppm shifts in HNMR analysis of paramagnetic compounds?

In H-NMR spectra of paramagnetic metal acetylacetonate compounds M(III)(acac)3, large ppm shifts are observed. This is seen with other organometallic compounds as well. What is the origin of this ...
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0answers
18 views

Four-velocity of particle in crossed E and B fields

The equation of motion for a charged particle in an EM field is given by (ignoring factors of $c$ throughout) $$\frac{d U^{\mu}}{d \tau}=\frac{e}{m} F^{\mu \nu} U_{\nu}$$ with $U^{\mu}$ being the 4-...
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0answers
16 views

How do I connect this 2V Diode to my circuit to fullfill the given requirements?

So I am struggling a bit with an excercise. "Your task is to make a red diode light up by connecting it to a voltage source of 12V. The current through the diode should be 10mA, and then voltage ...
1
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1answer
27 views

The description of a universe with one or two objects

I understand that in general relativity, we describe the universe by the relationship between objects "in it". I quote "in it" because in this model, there is no background where the objects exist. ...
1
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1answer
28 views

Why can we use Gauss' law to show that the field inside a spherical shell is zero?

I've read through the standard explanation of the electric field due to a spherical shell with uniform charge density. This explanation argues that because a Gaussian surface inside the shell encloses ...
-4
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0answers
21 views

Does Quantum Eraser erases results from past ( like we can prove by carbon dating etc )?

is it proven by Carbon - dating? [ by this I want to understand that particles actually see future ] Is there any proof that does it with techniques like carbon-dating?
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13 views

Deriving Fresnel Equations for parallel polarization using Maxwell's boundary conditions

I'd first like to preface this post with the "right answer" per wikipedia (I've seen the same answer elsewhere on more reputable websites) The thing I find trouble some is the cross terms such as $...
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0answers
9 views

How I can get the numerical factor in the relation between string coupling and YM coupling?

I'm trying to understand some references about Wilson loops being used to test AdS/CFT. Some of them are https://arxiv.org/abs/hep-th/0010274v2 https://aip.scitation.org/doi/abs/10.1063/1.1454377 ...
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0answers
5 views

Derivation of the wave field from an impulsive planar source

The figure shows the geometry for deriving the wave field from an impulsive planar source. The impulse is approximated by a rectangle $c\epsilon$ wide and $\alpha=\frac{1}{c\epsilon}$ high so the ...
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0answers
15 views

Gravity in a spacetime with 2 indistinguishable dimensions, with all spacetime directions equivalent

A spacetime with 2 indistinguishable dimensions and all spacetime directions equivalent would have the signature (++) meaning that there would be no difference between spacelike and timelike ...
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0answers
14 views

Partition function of a two level system

So I have a system made up of $N$ indistinguishable fermions that interact with each other. Also, the system is made up of two energy levels, and their gap is $D$. Therefore, trying to write down ...
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0answers
11 views

Steady flow for relativistic dust - stress-energy tensor

Given relativistic dust (p=0) in flat spacetime. The dust moves in one direction along coordinate $x$ only. Consider this flow is steady. So for a observer fixed at point $x_0$ $v(x_0)$ does not vary ...
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2answers
25 views

Representation of $SU(2)$, i.e., spin

Let \begin{equation} X= \begin{bmatrix} 0 & 1\\ 0 & 0\\ \end{bmatrix}, \qquad Y= \begin{bmatrix} 0 & 0\\ 1 & 0\\ \end{bmatrix}, \qquad H= \begin{bmatrix} 1 & 0\\ 0 & -1\\ \end{...
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0answers
25 views

Is quantum which-way information the real cause? [on hold]

I say all that matters is state. Which-way has nothing to do with it. State change is something that happens to a particle while in flight. The final panel is wave collapse and doesn't effect the ...
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0answers
28 views

Gravity as part of the metric but not of a 4-vector potential

In class, I've been told that the scalar potential $V(x)$ (except the one associated to gravity) has to be introduced in the Lagrangian as the time-component of a 4-vector potential $A_\mu$, so what ...
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0answers
7 views

Transformation to get rid of distribution multiplets

Are there any well-known distribution transformations that account for doublets, triplets, higher multiplets due to time series independent peaks occasionally being too close to resolve? I feel like ...
1
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0answers
30 views

Factor of 1/3 in diffusion constant

In Feynman's Lectures on Physics, it says that the diffusion constant for a diffusive gas may be written as $$D=\frac{1}{3}lv$$ where $D$ is the diffusion constant, $l$ is the mean free path between ...
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0answers
8 views

How does meson exchange work within super heavy nuclei?

I read the wikipedia page on Mesons and it mentioned that there both charged and uncharged Mesons that decay into neutrino/electrons and photons, respectively. Unfortunately it didn't elaborate on ...
1
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3answers
38 views

Why do we feel a force in circular motion?

I'm wondering why we only feel the centrifugal force in a circular motion. I did look at Why do we only feel the centrifugal force? question which is exactly that, but I'm not really satisfied with ...
2
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0answers
13 views

Interference in “Frustrated Two photon Creation”

In this paper it is explained how an SPDC source can have its emission inhibited by destructive interference with emission from a previous time. I have had a (maybe incorrect?) general intuition ...
4
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1answer
38 views

Geodesic equation in Einstein-Cartan manifold

In GR we use the Riemannian manifold without any torsion to describe the theory. Hence, the geodesic equation can be interpreted as "a trajectory of a free falling particle" or "equation of motion". ...
2
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3answers
41 views

Will a can filled with vacuum move when we let in air? [duplicate]

This picture is from L.C.Epstein's book Thinking Physics. The upper can is filled with compressed air, and, when an opening is made on the right, the air comes out and the can shoots left. The ...
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0answers
28 views

Michelson-Morley's experiment - neglecting gravity?

Michelson and Morley's experiment, together with other experiments, was determinant to establish one of the postulates of Einstein's special relativity, namely that the speed of light is the same in ...
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1answer
17 views

What happens to net acceleration in a non-inertial reference frame with cenripetal force?

In a non-inertial reference frame, the centripetal force is balanced by a centrifugal force. Therefore, shouldn't the net acceleration be zero? Yet, you still feel an acceleration outwards? Why is ...
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0answers
15 views

Is there a first-order formulation of CP-violating QCD?

In QCD without a CP violating $\theta$ term, (I believe) we can express the gauge kinetic Lagrangian in a first-order form with the field strength $F_{\mu\nu}$ taken to be Lagrange multipliers. Up to ...
-3
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2answers
80 views

Do electromagnetic waves exist outside the electromagnetic spectrum?

For example, the wavelength of radio wave ranges from 1 millimeter to 100 kilometers. Does any electromagnetic radiation exist which has wavelength more than 100 kilometers? If not, why?
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0answers
10 views

Spring restoring force vs applied force

Assume a compression spring with K= 1 N/mm. So when a force of 10 N is applied, spring compresses by 10 mm. Suppose at this position spring is locked or arrested and after some time, to compress the ...
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1answer
24 views

Spinthariscope with Uranium pottery / marbles instead of Americium

Usually home made zync sulfide spinthariscopes employ Americium 241 from smoke detectors as an alpha radiation source. Uranium glazed pottery (e g. fiestaware) and uranium 'glow in the dark' marbles ...
0
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1answer
31 views

Equation in Current vector in a Klein Gordon Equation

I'm trying to get the current vector $J^\mu$ of a Klein-Gordon equation: $$\Psi^* \Box \Psi =\Psi^* \partial^{\mu} \partial_\mu \Psi= \partial^{\mu}(\Psi^*\partial_\mu \Psi)-\partial^\mu \Psi^*\...
0
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2answers
30 views

How does Cosmic microwave background radiation provide temperature to the outer space?

We define temperature as average kinetic energy of atoms. We know that outer space has vacuum that is it lacks matter and hence the temperature should be 0 K. But because of CMB radiation, the ...
1
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1answer
17 views

Cylinder rolling down an incline in a vacuum

Say you set up an experiment with an inclined plane, and a cylinder rolling down the plane. Let's also let the experiment happen in a vacuum, such that there is no air friction. However, let there be ...
0
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3answers
34 views

How the ladder will slip if the wall and ground were to be smooth?

If I have a situation like this Where my blue thing is wall and the yellow thing is the ground. If both were to be smooth then they will exert a contact force only normal to them which I have ...
0
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1answer
46 views

In quantum mechanics, which concept caters for light rays?

If photon wavefunctions are omnidirectional and don't have a definite size, how comes those from the Sun don't all collapse on Mercury and some do actually reach Earth ? I understand that ...
2
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5answers
123 views

If an object moving in a circle experiences centripetal force, then doesn't it also experience centrifugal force, because of Newton's third law?

When an object moves in a circle, there's an acceleration towards the center of the circle, the centripetal acceleration, which also gives us the centrifugal force (since $F = ma$ is the equation for ...
-1
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0answers
17 views

How to go about solving this question? [on hold]

This question is from first order circuit and under the heading of source free RL circuit (https://i.stack.imgur.com/SY1L6.jpg)
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0answers
13 views

when assembly of atoms is influenced by em wave only few of them get excited not all? why?

In laser when assembly of atoms is influenced by em wave, only few of the atoms get excited not all? why it happens
-5
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0answers
52 views

Does shining a neutron beam with Xrays/photons of pair production potential > 1.022MeV accelerate neutron decay? [on hold]

Confirmed experimental data is the looked after answer. Pure, simple , straight forward. edit: beamed or bottled/cold neutrons, either works.
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0answers
34 views

At what angle is a rock thrown if the maximum height of its flight is equal to its horizontal range R? [on hold]

A rock is thrown upward from level ground in such a way that the maximum height of its flight is equal to its horizontal range R. At what angle $\theta$ is the rock thrown? I used range formula $R=\...
1
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0answers
32 views

Double-slit experiment with erasing all the collected data

The question concerns the double-slit experiment with collecting the data to register through which of the slits every single photon has passed. As I understand, in this case, when the photons are ...

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