# All Questions

134,964 questions
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 ...
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:...
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 ...
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 ...
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 ...
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 ...
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?
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 ...
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 ...
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 ...
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 ...
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 ...
43 views

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 ...
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 ...
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?...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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....
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? ...
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.

15 30 50 per page