# All Questions

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### What would be the displacement-time graph for a body dropped from a certain height which bounces back to the same height after hitting a surface? [closed]

For a freely falling object, displacement-time graph looks like this: When we observe the motion of a ball thrown upwards, the graph looks like this: When the ball moves upwards retardation occurs ...
37 views

### When is the Lagrangian a Lorentz scalar?

The Lagrangian $\mathcal{L}$ can be defined as the Legendre transform (when it exists) of the Hamiltonian $\mathcal{H}$, a non-Lorentz scalar quantity (as $\mathcal{H} =T^{00}$). My questions are, ...
1 vote
12 views

### Connection between dispersion relation and symmetries of the Hamiltonian

I am having trouble understanding intuitively the connection between the dispersion relation and the symmetries of the Hamiltonian. For example, suppose we have a lattice and there are four sub-...
14 views

### Magnetic Field - 2 types

i have just started studying magnetism in electrostatics, electric field exists. Is there a magnetic counterpart for this, if so then what is it, what is its unit and how do we define it ? Is this ...
1 vote
20 views

### Does electric and magnetic field from electromagnetic radiation are 2D based?

I'm getting into physics, specially in electromagnetism. When we're talking about electromagnetic radiation. Does it has a 2D shape when it's propagating through space? Does Maxwell's equations ...
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29 views

### Magnetic Field Generation in a Vacuum Through Special Relativity

The way special relativity explains electromagnetism is that when electrons move, their lengths contract due to relativistic effects, even though they do not move at extremely high speeds. This ...
18 views

### Calculating Binding Energy of Th 230 nucleus

Ok this is NOT a homework question. But it’s somewhat related. Please bear with me. In calculating BE of Th 230, I used the rest mass of proton as 1.007276u and rest mass of neutron as 1.008665u (as ...
61 views

### Wikipedia states that the relativistic Doppler effect is the same whether it is the source or the receiver that is stationary. Can this be true?

According to Wikipedia, the relativistic Doppler effect is simply the classical Doppler effect for a stationary source, $1-v/c$, times the relativistic time dilation, $1/\sqrt{1-v^2/c^2}$ (where v is ...
27 views

### Passive transformation confusion [closed]

I'm reading Group Theory by A. Zee, specifically, chapter I.3 on rotations. He used the passive transformation in analyzing a point $P$ in space. Two observers, one labeled by unprimed coordinates ...
• 404
25 views

### Question regarding friction acting on a disk on a conveyor belt [closed]

I have the following problem on which i am working A horizontal conveyor belt is running at a constant speed of $v_b = 3.0\hspace{1mm}m/s$. A small disc enter the belt moving horizontally with a ...
50 views

### Time evolution of state in first and second quantization

I was trying to work out the time evolution of a single particle state in second quantization and got something apparently contradicting with the first quantized picture. For a system with energy ...
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22 views

### If system and block are released from rest, find the tension in string when the string is vertical [closed]

By using Work Energy Theorem, as well as Velocity of centre of mass, I succeeded in finding the velocities of both the ring as well as block. I noticed that there is going to be a vertical circular ...
36 views

### Strogatz's condition on definition of energy

In, Nonlinear Dynamics And Chaos, 2nd edition page 160, by Steven H. Strogatz, he writes Let’s be a bit more general and precise. Given a system $$\dot x =f(x),$$ a conserved quantity is a real-...
17 views

### Calculating tension in a pressurized container [closed]

Suppose I have a pressurized spherical container made of 1 mm thick aluminum. The container has pressure P and internal volume V. How would I calculate the tension in the aluminum? The aim of this is ...
50 views

### Why Consider Only Triplet States for Spin in $2$-Electron Systems?

I have a question regarding systems of 2 electrons and their spin properties. When the Hamiltonian of a system of 2 electrons can be written as a sum of two single-particle Hamiltonians that are ...
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41 views

### What is Suvrat Raju's point of view towards information paradox? Is it accepted by others? [closed]

Wondering what's the gist of his idea https://arxiv.org/abs/2012.05770 https://www.suvratraju.net/classes/black-hole-information-paradox/materials/lecture-1-introduction-and-two-point-qft-cor
27 views

### Field theories where the potential solves a linear Schrodinger equation

Are there physical situations/applications where the potential solves a linear time-dependent Schrodinger equation, or where the gradient of a solution to the Schrodinger equation (after somehow ...
23 views

### Pressure at a point around the corner in a conical fask

I have gone through this two very informative links in understanding pressure. Weight of fluid in a conical container act entirely on the base? Pressure is isotropic But in a long conical flask which ...
62 views

### Do Helium-4 atoms behave like photons?

I know that the Helium-4 atom is a boson. Does this mean that, like photons, many Helium-4 atoms can be placed at the same point in space? How its possible? It includes fermions (Protons, Neutrons, ...
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8 views

### Finding out the number of minima for a fourier expansion [migrated]

Suppose I have a Fourier series f(x) = $\sum_{n=1}^N t_n cos(nx)$ defined in the domain $(-\pi,\pi]$. we need to prove that mathematically we can ' at most' have N minima points excluding the boundary ...
40 views

### Calculating the expectation value of the angular momentum operator

I'm not looking for the exact answer to the question, but rather why a certain way of solving it is chosen. We agree on the answer, but why is the approach different. I'm afraid it's a sign of me not ...
49 views

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