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How to determine the speed and acceleration of an item moving vertically when another item moves horizontally? [closed]

A horse lifts a bucket with a rope and a pulley. Find the velocity $v_{a}(x)$ and acceleration $a_{A}(x)$ in terms of $x$. How do I go about solving this? What is wrong in my attempt?
55 views

Eigensystem of part of the representation of the position operator: $a^\dagger+a$ in the base of the quantum harmonic oscillator [closed]

What are the exact eigenvalues and eigenvectors of the following matrix? \begin{pmatrix} 0&\sqrt{n}&0&\cdots&0&0\\ \sqrt{n}&0&\sqrt{n+1}&\cdots&0&...
641 views

Photon propagator in path integral vs. operator formalism

I am self-studying the book "Quantum field theory and the standard model" by Schwartz, and I am really confused about the derivation of the Photon propagator on page 128-129. He starts ...
• 593
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Modeling centrifugal distortion with an effective charge distribution

The hamiltonian of a rigid object with a totally symmetric moment of inertia (i.e. a "spherical top") will depend only on the magnitude of its angular momentum. If we allow the object to ...
• 722
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Some questions regarding a pulley [closed]

Please have a look at the following diagram sketched by my Professor. The points $P_1$ and $P_2$ have mass $m_1$ and $m_2$ respectively . The pulley is frictionless and it is represented by a ...
64 views

As I read an article on this website that light cannot warp space time fabric [closed]

But actually we know that energy is equals to mass then light energy can act like mass and it can create a black hole made up of light . As per Einstein equation E=mc² then why there is no black hole ...
144 views

Why won't there be any transfer of heat energy when ice at 0°C is in contact with water at 0°C in a closed container?

In my book, Concise Physics of Selina Publications for Class IX, it's written there that "If there is no transfer of heat between the two bodies placed in contact, they are said to be at the same ...
36 views

How does Shear Force on a fluid in a vessel reaches an equilibrium if molecules are free to make contact?

In Hydrostatic, if the fluid is a perfect fluid that is non-viscous, it doesn't experience any shear force because if it would experience so it might start flowing so something might be working to ...
47 views

Why the frequency component is not included when the energy of a wave is described?

Energy of a wave is directly proportional to its Amplitude squared. There is no inclusion of frequency in it. But by intuition if one thinks about it, isn't it obvious that a wave with higher ...
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Magnetic Dipole Derivation

$\oint (\hat{r}\cdot \vec{r}') d\vec{l}$ is what I get as part of the magnetic dipole term, but I can reduce this to $-\vec{r}' \times \int d\vec{a}'$. I don't understand how you can reduce it to ...
58 views

Bohmian mechanics, Leggett inequality, realism and nonlocality

Very often it is said that the Bell inequality has ruled out the possibility of hidden variables (HV) in QM. This is incorrect since Bell inequality has ruled out local hidden variables: nonlocal HV ...
• 283
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End points of event horizon

I am reading The Nature of Space and Time by S. W. Hawking. In the last paragraph on page 16 he said that: event horizon may have past end points but don't have any future end points I understand ...
1 vote
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Could a single gamma ray photon break the Schwinger limit? If so, at what energy?

Is it possible for a ray of light, or even a single photon, to 'break' the vacuum of space? If so, at what energies (in eV, e.g.) would this happen?
• 4,509
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Is there a straightforward simplified proof of energy conservation from time translation symmetry?

Electric charge conservation is easily proven from electric potential gauge symmetry, as follows: The potential energy of an electric charge is proportional to the electric potential at its location. ...
69 views

Is my simplified explanation of Volts vs Current correct? [closed]

I was struggling to find any meaningful difference between Volts and Current, when studying the basics of Ohm's law. The sentences explaining Potential Difference, between the negative and positive ...
54 views

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 ...
136 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
22 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-...
1 vote
39 views

Does electric and magnetic field from electromagnetic radiation are 2D based? [closed]

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 ...
• 11
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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 ...
32 views

Calculating Binding Energy of Th 230 nucleus [duplicate]

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 ...
4k 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 ...
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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 ...
66 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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47 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-...
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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 ...
82 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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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
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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 ...
37 views

Pressure at a point around the corner in a conical fask [duplicate]

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 ...
1 vote
86 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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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 ...