0
votes
1answer
7 views

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 ...
-1
votes
1answer
12 views

Contradictory kinematics formula

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 ...
1
vote
0answers
7 views

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 ...
0
votes
0answers
27 views

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 ...
4
votes
3answers
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 ...
-2
votes
1answer
12 views

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
4
votes
2answers
241 views

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 ...
0
votes
0answers
5 views

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 ...
0
votes
0answers
10 views

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 ...
0
votes
0answers
4 views

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'...
2
votes
8answers
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 ...
2
votes
1answer
45 views

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 ...
7
votes
2answers
94 views

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 ...
0
votes
1answer
18 views

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 $295^\circ$?
0
votes
0answers
6 views

Selection rules for electric quadrupole radiation

The selection rules for electric quadrupole radiation in a Hydrogen-like atom are: $$ \begin{aligned} \Delta l &= 0,\pm2 \hspace{1cm}(l=0\leftrightarrow l'=0 \textrm{ is forbidden}) \\ \Delta m &...
0
votes
1answer
13 views

Can circular polarized light be cancelled?

I can cancel the light output from an LED screen by placing a linear polarizer at 90 degrees from the linear polarizer built into the LED display. OLED displays use circular polarizers instead of ...
4
votes
1answer
201 views

What equation predicts at what point a stretched object comes apart?

I am creating a simulation and am interested in pulling stretchy things and when they break, like taffy. I imagine this is a bit tougher then a simple equation like gravity, but I have no idea. Is ...
2
votes
2answers
304 views

Why do racing tires (slicks) provide more traction with the road?

Google: By eliminating any grooves cut into the tread, such tires provide the largest possible contact patch to the road, and maximize traction for any given tire dimension. My understanding is that ...
6
votes
2answers
124 views

Why do some types of waves disperse?

We know that some mediums/waves are non-dispersive such as air for sound waves, and waves on a string. But, why do some waves, for example deep water waves, disperse? I am trying to understand the ...
3
votes
2answers
175 views

Problem with derivation of phonons in crystal

In this derivation of phonon solutions, everywhere, we are forcefully assuming the wavelike characteristics along the length of the chain. While all we can deduce for finding out the fundamental ...
0
votes
1answer
26 views

Time reversal symmetry for non-orientable manifold

From a recent paper by Kapustin(https://arxiv.org/abs/1406.7329), he argued that for non-orientable manifold with spin structure $Pin^{\pm}$, the corresponding time reversal symmetry $T$ squares to ${...
2
votes
1answer
20 views

Shared electron behaviour in a covalent bond

Some basic questions: 1) I can't figure out how two atoms form a covalent bond. We say two atoms make a covalent bond when they share an electron. On the other hand, we know that electrons circulate ...
0
votes
0answers
14 views

Before Dark Energy was discovered

I'm really confused on this topic. Pardon my French if my questions seem really stupid. Before Dark Energy was discovered in 1998 did scientists know that the cosmological constant calculated, I ...
2
votes
0answers
9 views

Does the vacuum have a zero Seebeck coefficient?

I was considering how at very high energies (e.g the Schwinger Limit) the vacuum starts having properties we would normally associate with "materials", such as non-linear polarizibility. The Seebeck ...
1
vote
0answers
27 views

Why do we add gamma to derive the Lorentz transformation?

I was trying to derive the Lorentz transformation with the following... $$\frac{t'}{t} = \frac{c-v}{c},\qquad \frac{t}{t'} = \frac{c+v}{c}$$ After adding gamma $$\frac{t'}{t} = \gamma\frac{c-v}{c},\...
0
votes
0answers
34 views

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 ...
0
votes
1answer
20 views

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. ...
1
vote
2answers
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 ...
-5
votes
0answers
16 views

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
1
vote
0answers
27 views

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 ...
3
votes
1answer
13 views

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 ...
3
votes
2answers
53 views

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 ...
0
votes
1answer
19 views

Curious about headphones

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 (...
0
votes
0answers
286 views

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 ...
1
vote
1answer
91 views

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, ...
0
votes
3answers
110 views

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 ...
3
votes
1answer
31 views

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 ...
2
votes
1answer
87 views

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 ...
5
votes
7answers
2k views

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.
1
vote
1answer
385 views

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 ...
-1
votes
0answers
22 views

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 ...
0
votes
0answers
26 views

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)....
0
votes
2answers
47 views

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 ...
8
votes
3answers
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 ...
9
votes
2answers
421 views
+200

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 ...
3
votes
1answer
122 views

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, ...
-2
votes
0answers
53 views

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 ...
-1
votes
0answers
50 views

Probability density of a trig function [on hold]

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 ...
0
votes
1answer
49 views

Applying angular momentum operator

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 ...

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