All Questions

0
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0answers
7 views

Displacement currents in the air or in the soil?

Can there be a displacement currents in the air and if yes, can they transfer any significant energy on a relatively long distances? Something like 50-100 meters? What could be an efficient way to ...
0
votes
0answers
5 views

How do I find the pulling force required to lift an object in a system of 3 pulleys?

In the image above, assume that the person is lifting the 12.5 kg weight at a constant velocity and the pulleys are frictionless. In this case, what would the pulling force be? Here's what I've tried:...
0
votes
1answer
8 views

Why a softer phonon is easier to get excited

In Kittel's book, "Some other structure B may have a softer or lower frequency phonon spectrum than A. As the temperature is increased the phonons in B will be more highly excited (higher thermal ...
0
votes
0answers
3 views

In a pilot-wave model, is knowing the position of the particle sufficient for predicting its behavior?

Suppose that we somehow exactly know the position of an electron before hitting the double-slit structure (for example we know it's 20cm away from the structure and it's closer to the left slit). In ...
0
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0answers
12 views

No friction in pure rolling - how about driving a car?

I remember the un-intuitive result that pure rolling without acceleration involves no friction by the law of conservation of angular momentum. Conjectures: I understand that when I'm driving a car at ...
0
votes
2answers
33 views

Kinetic Energy - dependence of mass

There are 2 equations to kinetic energy: $\frac{1}{2} mv^2$ and $\frac{3}{2} kT$. By the first equation kinetic energy depends on mass, while by the second one it doesn't. How comes? So does it ...
0
votes
0answers
18 views

Does everything and anything have weight or mass. In other words can we measure everything we know?

My question related mostly to a thing such as a thought. How can we weigh that?
-1
votes
0answers
10 views

Is travelling in the past is possible? [on hold]

I disagree with Einstein who stated that going to the past is not possible by stating his Grandfather's paradox theory which says that if one goes to the past and kills his/her grandfather then how ...
0
votes
0answers
9 views

What happens to pressure when a liquid turns into a gas in a confined chamber?

I'm doing an experiment requiring immense pressures. Since I do not have access to a pump that can create these pressures I settled on something different... Instead of using a pump I want to utilize ...
0
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0answers
22 views

Lie algebra: Proof that the commutator of infinitesimal motions is an infinitesimal motion

I am following Classical and Quantum Mechanics via Lie Algebras by Neumaier and Westra. Setup I am stuck at part of Thm 2.3.1. Consider the matrix group $\mathbb{G}$. The set of $\mathbb{G}$-motions ...
-1
votes
0answers
14 views

Two uniform solid cylinders a and b [on hold]

Two uniform solid cylinders a and b each of mass 1 kg connect by light spring of force constant 200 n/m at their axles and are placed on a fixed wedge as shown in figure.the coefficient of friction ...
0
votes
0answers
22 views

Gauge transformation [on hold]

We consider a particle with charge $q$, the Hamiltonian $H$, potential function $V(x,t)$ and the vector potential $\vec{A}(x , t)$. The evolution of the wave function $\Psi (\vec{r}, t )$ is given by ...
0
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0answers
43 views

What is the role of $\hbar$ in quantum mechanics? [duplicate]

Planck's constant $\hbar$ appears in the Schrodinger equation: $$i\hbar \frac{d|\psi\rangle}{dt}\ = \hat{H}|\psi\rangle$$ which implies for stationary states, $$|\psi(x,t)\rangle=e^{-iE_n/\hbar}|\...
-6
votes
0answers
22 views

Is Einstein's Grandfather's theory is wrong? [on hold]

I claim that Einstein's Grandfather paradox theory is wrong. I find that Einstein told that if one goes to his past and kills his/her grandfather then where his/her existence is? Einstein claims from ...
0
votes
0answers
15 views

Mathematics of quantum mechanics for beam splitter

I'm reading a book where quantum interference is explained with a common experiment, where photons are thrown to some apparatus formed by two beam splitters: Describing the problem using linear ...
0
votes
0answers
14 views

Alternative paradigm for the universe indistinguishable from current paradigm ? Why so?

How can a universe with fixed size and a speed of light inversely proportional to time since creation be differentiated from the current expanding universe paradigm? The speed being infinite a T=0 is ...
2
votes
1answer
26 views

Complex conjugated representation and its Young tableaux

This post is an exact copy of one that I posted in Math's site. I do this copy because people there suggested me to do it since, apparentely, in Mathematics and Physics we use different conventions ...
0
votes
1answer
25 views

Gravitation and escape speed

I applied conservation of energy at the surface and at the centre of earth which brought me too equation ''- GMm/R =1/2 m v^2 '' having asked my sir he said that gravitational potential energy at the ...
-1
votes
0answers
15 views

How can an electric field between two parallel plates be constant

How can electric field in general and more specifically between two parallel plates be constant, if E depends on distance, how can the electric field be constant. The equation deltaV=Ed, should E not ...
0
votes
1answer
16 views

Infinitesimal parameter of Lorentz transformation

I'm working through the SUSY lecture notes by Lambert, and he does something which seems strange to me during the calculation of the Wess Zumino model. He says the spinor $\psi$ has the ...
0
votes
0answers
20 views

Speed of the weight? [on hold]

a) If the 20-kg cylinder is released from rest at h = 0, determine the required stiffness k of each spring so that its motion is arrested or stops when h = 0.5 m. Each spring has an unstretched length ...
-1
votes
0answers
9 views

How to proof that invisiable metter is not simply function from (visiable mass, time) pair?

How to proof that invisiable metter (Dark Matter, Dark Energy) is not simply function from (visiable metter, universe age) pair in terms of known laws of phisics?
0
votes
0answers
23 views

Diffraction due to thin wire [on hold]

Here's what I did: The wire ends can be taken as two slits So $$θ=λ/d $$ $$2θ=λ/d $$ So we have $$s=r2θ $$ The relationship between x and s is $$(x/s)=sin(2θ/2) $$ r, θ and (a+b) are a part of the ...
0
votes
1answer
18 views

Confusion of the Isobraic Process Heat equation

I was currently reading a wiki article on Isobaric Process (Link at bottom f post). And am confused as to why in there derivation of heat of a an isobaric system they use specific heat capacity for ...
0
votes
0answers
12 views

Rotational Motion of a thin disc

A thin heavy disc can turn freely, about an axis in its own plane, and this revolves horizontally with a uniform angular velocity $\omega$ about a fixed point on itself. Show that the inclination $\...
0
votes
1answer
26 views

Does the Uehling potential have any observable effect?

Uehling potential is the correction made to the coulomb potential due to vacuum polarization (electron-positron pair creation and annihilation). How big is this correction compared to the coulomb ...
1
vote
1answer
10 views

Newton's rings. Interference by division of amplitude

We all know that in wedge shaped film fringes are equally spaced.Being a wedge shaped film Why does the fringe width decrease as order increase in Newton`s ring ?
0
votes
0answers
25 views

Levi-Civita identity [on hold]

with Einstein summation convention What's my problem?
2
votes
1answer
69 views

If infinitesimal transformations commute why dont the generators of the Lorentz group commute?

If infinitesimal transformations commute as proved eg here, why are the commutators for the generators of the Lorentz group nonzero?
0
votes
3answers
34 views

Orientation of resistor when connected in a cicuit

Consider a cuboid shaped resistor. Now Case1: Connect the resistor along is length to a battery. Case2: Connect the resistor along is breadth to a battery. In the two cases the length and cross-...
1
vote
0answers
24 views

Can neutronic emissions be used as a power source?

The free neutron will degrade to a proton electron and anti neutrino in about 15 minutes. Assuming you could slow a beam of free neutrons sufficiently to keep the size of the reactor manageable: Is ...
0
votes
0answers
7 views

What are the implications of a warmer earth for hurricanes by 2100?

The main magic number is the surface sea water temperature. Above, I think 27 C the warm, moist air provides more energy that the storm uses. This is why the hurricane season is late summer into ...
0
votes
1answer
36 views

How fast will air travel to fill a vacuum?

Suppose I have a sealed glass cylindrical vessel of radius r and length l that is evacuated. I smash one end. How long will it take for air to (a) reach the end of the cylinder (b) fill the vacuum ...
0
votes
0answers
20 views

Observing a comet and predicting its trajectory

I'm planning to observe a comet of apparent magnitude around 18.5 using an observatory telescope. I plan to figure out the trajectory of the comet - all its orbital elements. Given that I only know ...
0
votes
0answers
36 views

Symmetry acting on a complex fermion operator

Suppose $S$ is a $\mathbb{Z}_2$ symmetry operator, i.e. $S^2=1$, acting on the fermion $c_{n}$ via $$S c_{n} S^{-1} = \sum_{m} U_{nm} c_{m}$$ and I am interested in $S$ is both linear or anti linear, ...
0
votes
1answer
36 views

SR time dilation discussion meaningless when there is gravity?

Let us say you have three clocks fixed to the spinning earth at the equator. If you set one of this clocks on a plane going eastwards around the globe it will have measured a lesser amount of time ...
0
votes
1answer
38 views

The trouble with a singularity

As an engineer, we are taught that the root cause of any problem can be solved if we ask why 5 times. Sometimes you can figure it out at 4 and sometimes at 6, but it always averages to 5 times. - You ...
4
votes
0answers
45 views

What is a singular continuous spectrum?

I read some answers about this and the wikipedia page that basically always say that a spectrum can be decomposed into: $$\mu = \mu_{ac} + \mu_{sc} + \mu_{pp}, $$ where $\mu_{ac}$ is absolutely ...
0
votes
0answers
19 views

Representations of the SUSY algebra

I am currently reading Wess & Bagger, and have trouble with a statement they make about representations. If we wish to study massive, one-particle representations of the SUSY algebra, we boost to ...
0
votes
1answer
21 views

What comes out of binary black holes at end of inspiral?

When 2 blackholes are orbiting each other so close that they lose more energy in form of gravitational wave, this process is inspiral and is unstoppable until it explodes. This is an extremely violent ...
1
vote
0answers
26 views

How can I simulate the interactions of electrons?

Suppose I have a few electrons in a vacuum. I know the probability density of each of their positions. How can I calculate what their new probable positions will be a second later, after they interact?...
0
votes
0answers
30 views

Can a star visually look like a black hole? [duplicate]

Amateur question incoming so please bear with me. Assumptions If a black hole is born from a star going supernova, intuitively it should have the same or less mass compared to the star. Black holes ...
0
votes
1answer
29 views

Wavefunction of particle in rigid box when one of the wall (right) gets destroyed?

I have question, how can I solve problem of particle in rigid box when one of the wall gets completely destroyed? At time $t = 0$ the right wall of box gets completely destroyed, left wall is still ...
-1
votes
0answers
22 views

How would the bubbles behave if

If the whole universe was filled with water and there was only 2 bubbles present would they attract or repel. I guess they would attract because of surface tension but I am not totally sure why and ...
2
votes
4answers
175 views

Why electric field inside a cavity of a non-conducting sphere not zero?

Now consider a charged non conducting sphere of uniform charge density, and it as hole of some radius at the centre, now suppose I apply gauss law as there is no charge inside the cavity: so no ...
0
votes
0answers
10 views

What does the interferogram in Michelson interferometer mean about the topology of the specimen?

I'm want to know how can I evaluate the surface of a fibre by using the interferometer of Michelson. The object beam in this method is reflected from the object and combined with the reference beam to ...
0
votes
0answers
16 views

What creates the physical difference in ageing when travelling close to the speed of light? [duplicate]

I probably have a fundamental misunderstanding, so correct me if I'm wrong. When travelling close to the speed of light, movers experience time dilation, which is what results in the phenomenon of ...
0
votes
0answers
14 views

2 blocks On a slope [on hold]

hey I need help with this question I have this sketch and the tell me that m1= 2 kg, m2= 5 kg the say that we don't have friction between m2 and the floor the kinetic friction between m1 and m2 is 0....
1
vote
0answers
13 views

Book on tetrads formalism and tetradic formulation of General Relativity [duplicate]

Could anyone give me some references for mathematicians (coordinates free notation, formalism of fiber bundles etc.) about tetrads, Palatini-Cartan theory, stuff about formulation of GR with tetrads? ...
0
votes
0answers
23 views

Wave Characteristics [on hold]

I have been learning waves like for years now but still I feel pretty anxious about it. I know the definitions, equations and all but still I am not able to digest the concepts.

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