# All Questions

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### Reducing coefficient of friction by vibrations?

Very simply put, if one places a block of some material on a level surface and pushes it horizontally, a certain coefficient of friction is measured. If one tightly couples an oscillator of some sort ...
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The displacement of a particle in 't th' time is given by S(t)=u+(a/2)(2t-1).. The thing that contradicts this formula is tht it is dimensionally incorrect, if it is dimensionally incorrect then why ...
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### In quantum mechanics, how exactly do we associate Hermitian operators to classical observables?

In a first course on quantum mechanics, everybody learns some version of the following statement: Postulate: To every classical observable $A$ of a physical system, there corresponds a Hermitian ...
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### Does the use of $\gamma=\left(1-v^{2}/c^{2}\right)^{-1/2}$ automatically assume a (+ - - - ) metric?

In Special Relativity, does the use of $\gamma=\left(1-v^{2}/c^{2}\right)^{-1/2}$ automatically assume a (+ - - - ) metric convention? For introductory textbooks, the Lorentz factor is is always ...
297 views

### Spacetime and uncertainty principle

I only have limited knowledge of relativity and quantumphysics but as far as I know, the uncertainty principle relates the uncertainty of space and momentum of a particle. Einstein however, explained ...
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### Newton's 1st law

If all of a sudden the gravitational force and gravity disappears then the planets would still continue to rotate and revolve ? Give reason
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### Electric Field inside a diode

When a voltage is applied to a diode (Forward or Reversed bias) the depletion zone is changed due to charges change in this region. My question is in both case (Forward or Reversed bias), how the ...
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### Is the reduction of tensor loop integrals to scalar integrals using Passarino Veltman Functions, theory dependent?

While reducing the tensor integrals to scalar integrals all that we use are Lorentz covariance and the physical interpretation of the result. Thus I think that the Pa Ve Reduction of Tensor integrals ...
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### Publishing in American Journal of Physics

Can I publish my article in American Journal of Physics, if I am not a part of any educational/research institute nor a part of private industry ? Also I do not have any referee. Do I need to pay to ...
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### Second Law of Dynamics and Pulleys

The system in the figure is initially at rest . If the system starts to move , evaluate the acceleration of the block A. Mass of the block A = 60kg ; mass of block B = mass of block C = 20 kg. ( There'...
29k views

### Water pressure calculation for a volume of water at a given height

I'm looking to create a rain harvesting system. I have a 275 gallon IBC tote that is 48" x 40" x 46". I have an adapter for a 3/4 garden hose at the bottom of the IBC tote. I'm trying to figure out ...
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### Friction to just move the blocks

Two blocks each of mass $m$ are placed on a rough horizontal surface and connected by mass-less in-extensible string as shown.The coefficient of friction between each block and ground is $\mu$ What ...
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### What is “a general covariant formulation of newtonian mechanics”?

I am a little confused: I read that there are general covariant formulations of Newtonian mechanics (e.g. here). I always thought: 1) A theory is covariant with respect to a group of transformations ...
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### What is the meaning of a negative Galactic longitude?

What is the meaning of negative longitude in Galactic coordinate system? Does the longitude $-65^\circ$ equal $295^\circ$?
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### Work done by the battery in series with capacitor with changing dielectric

If we have a battery with voltage $V$ connected in series with a parallel-plate capacitor of capacitance $C$ with dielectric $\epsilon$,and then we pull the dielectric out, the infinitesimal work done ...
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### Dyson Sphere Structures [on hold]

In a type II civilization we may need to harvest the energy of neighboring stars. Freeman Dyson gave an interesting point of view that we could invent a megastructure to harvest this type of energy. ...
464 views

### Determining the neutral axis of an I-shaped cross section with dissimilar materials

Determine the neutral axis of the I- shaped cross section with dissimilar materials. The top rectangle of the cross section is made out of aluminum and the second and third part are titanium ( these ...
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### Answer true or false? [on hold]

True or false? Q: The magnitude of displacement is equal to distance covered in a given interval of time if the particle ___. A: moves with constant acceleration
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### Differential equation in RL-circuit

I am self-studying electromagnetism right now (by reading University Physics 13th edition) and for some reason I always want to understand things in a crystalclear way and in depth. Now look at this ...
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### Laser speckle reduction for integration time of microseconds

How to reduce laser speckle noise for an imaging system that demands integration times of microseconds? I am aware of these two commercial solutions: Optotune laser speckle reducer. It has a ...
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### Can we see/detect things which don't have electrons

Whenever we sees a thing the process happening at atomic level is the electrons of that stuff absorbs the energy from packets and goes to higher state and then comes to ground state and emits ...
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So I'm trying to learn more about headphones. I have a small piston that is in a small sealed volume (the earcup, say it is $25\, cc$). And there is a front volume between the piston and the ear (...
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### Could dark matter/dark energy turn out to be tachyonic?

Today, I was watching the Inexplicable Universe with Neil deGrasse Tyson. He spoke about Dark Matter, Dark Energy, and then he spoke about Tachyons. Naively, I thought what if the reason we can't ...
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### Is $A_\mu A^\mu=0$ a good gauge fixing?

I am taking a course in classical electrodynamics and I am facing this problem Prove that $A_\mu A^\mu=0$ is a good gauge fixing or not. If it is, there are residual gauge freedom? I know that, ...
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### Work in the First Law of Thermodynamics

The First Law can be stated as $\Delta U=Q-W$, where $W$ is the work done by the system. My question is what kind of work $W$ includes. $W$ certainly includes $PV$ work, i.e. expansion and compression ...
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### Inflaton Decay Rate

After inflation, (p)reheating is supposed as the mechanism which is responsible for restoring hot Big Bang. Always the resulting decay rate of inflatons into bosons and fermions are mentioned without ...
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### How to evaluate possible values of spin of two photon system?

Photon hasn't well defined quantity such as spin. Instead of it, it is characterized by helicity $h$. Let's assume state of two photons in CM frame (with $\mathbf k$ being the momentum of one of ...
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### Is it possible to destroy proton in proton-proton collision?

Or in proton-electron collision. To destroy is to turn into other particles, not baryons. In context of the baryon asymmetry.
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### Magnitude of the average velocity vector (not the average speed)

Thank you ahead of time for taking to look at this. For this following problem we were given an answer however I am almost positive the given answer is wrong. It doesn't even make sense. So here is ...
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### Why does a charged parallel-plate capacitor with infinitely large area on both plates never discharge? [on hold]

Alternatively, as the distance between the plates in a charged capacitor approaches zero, Coulomb force becomes greater and greater. How can it be discharged if there's such strong attraction? Both ...
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### Double Atwood machine alternate solution is wrong?

** NOTE I cannot post multiple links due to reputation so here is my reference link.** I came across a double atwood machine problem where we were to find the acceleration of each mass(image in link)....
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### How do we determine the location of particles?

Can someone explain how the location of a particle is determined both theoretically and experimentally (if possible)? Can the location of a particle be given by the uncertainty principle? (dividing ...
9k views

### Would being underwater help survive a nuclear bomb?

If I jump in my pool, on the river near my house knowing that a nuclear bomb, or atomic or H-Bomb exploded around 10 km from my house, would I survive? The way I see it is that water will protect me ...
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### Why does water ($\mathrm{H_2O}$) only have two distinct fluid phases?

Water (and other substances) can exist in many distinct solid phases (with different crystallic micro-structure), but only in two fluid phases - liquid and gaseous, in which the molecules are oriented ...
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### Is meters per second equivalent to seconds per meter?

I know this question is probably ridiculous, but bear with me for a moment. This thought emerged while I was converting between nm and wave numbers ($\rm cm^{-1}$). In order to prove this conversion, ...
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### What does the Free Will Theorem Imply?

Sorry if discussion of the Free Will Theorem belongs in the philosophy section, but as it is in the realm of physics too, I thought I would post it here instead... If we have a free will in the ...
I have a problem: I'm given that the needle on a speedometer is broken, free to move, and equally likely to be found at any point between $0 < \theta < \pi$ So, obviously the probability ...
How are the algebraic steps to applied the angular momentum operator defined as: $$\hat{L}=-i\hbar[r\times\nabla]$$ to $$\Psi=a~ \psi_{431}$$ where the $\psi_{nlm}$ are the eigenfunctions of the time ...