-2
votes
1answer
37 views

Gravitational Time Dilation Formula? [on hold]

What is the equation for calculating the dilation of time at different levels of gravitational force?
1
vote
0answers
14 views

Is work done on a fluid in a communicating vessel necessarily equal to work done by the fluid inside it?

During the explanation of Pascal's law the argument that work done by a force to move the fluid inside communicating vessel is equal to the work done by the fluid at the other end of the vessel was ...
4
votes
3answers
85 views

Is acceleration caused by curvature or space or time or both?

I'm trying to get a hold of the idea of gravity in general relativity and spacetime. I've seen plenty of demonstrations of the rubber mat analogy to describe gravity and spacetime curvature. Is this ...
-1
votes
0answers
14 views

Calculate the attenuation constant on a lossy transmission line [on hold]

$\nu$ = 10 [kHz] $L$ = 600 [nH/meter] $R$ = 50 [mOhm/meter] $C$ = 80 [pF/m] $G$ = 0 So the question on my test was what is $\alpha$, the attenuation constant? The answer is $\alpha$ = 0.25 [1/km] ...
0
votes
2answers
32 views

What are the hypothetic cases when entropy of a closed system may decrease? [on hold]

What are the hypothetical possibilities that entropy of a closed system may decrease? I would accept plausible but hypothetical setups. For instance, Non-trivial timeline topology (closed timelike ...
0
votes
0answers
22 views

Extreme temperatures, relativity and kinetic theory

According to kinetic theory, average kinetic energy is proportional to temperature. Supposing $k_BT/2$ per particle, can we use relativity and kinetic theory to calculate, e.g., the temperature and ...
1
vote
0answers
40 views

How did Rayleigh and Jeans apply the Equipartition of Energy in determining the energy distribution of blackbody - radiation? [duplicate]

I am reading the Ultraviolet Catastrophe and have come across this law. Here , it is written They applied the statistical physics method to the waves by analogy with Maxwell's gas particles using ...
1
vote
3answers
63 views

Why does the blackbody radiate even at thermal equilibrium?

Everytime, I read about blackbody, I always get confused at the point where it is written Under thermal equilibrium conditions , the blackbody radiation depends only on temperature. ..... . At ...
0
votes
2answers
53 views

Why need for 96kHz, 192kHz audio? [on hold]

Human can hear 20-20,000 Hz waves, so by Nyquist theorem it's sufficient to sample audio with 40 kHz. Indeed, 44.1 kHz widely used. But what do we need higher sample rates for? 96 kHz, 192 kHz are ...
0
votes
0answers
33 views

Which foods provide a human with most energy per gram in weight? [on hold]

I just read about an astronaut who took 5KG of Caviar into space (not related to cost as far as I know) but it got me thinking, since it costs so much money to send things into space, which foods ...
2
votes
0answers
39 views

Relationship between Liouvile's theorem and Diffusion equation

Consider a Hamiltonian system. According to the Liouville's theorem there exists a probability density function $\rho(q^a,p_a,t)$ in the phase space whose evolution is given by $$ \frac{\partial \rho ...
14
votes
6answers
5k views

Can a car steer on a frictionless surface?

Do the front tires of a car act like gyroscopes, such that a car could steer on a frictionless surface?
1
vote
0answers
30 views

Does the total energy in an electromagnetic field depend on the acceleration of the sources?

If I accelerate a charge from rest to some velocity $\vec v$, does the total final electromagnetic energy contained in the field depend upon the acceleration of the charge?
-2
votes
1answer
33 views

What Maxwell done on the Faraday's law and Amper's law and Gauss's law which famous by Maxwell's equations? [on hold]

What Maxwell done on the Faraday's law and Ampere's law and Gauss's law which famous by Maxwell's equations?
1
vote
0answers
44 views

Do time dilation tests prove that it exists or that atomic clocks are faulty? [duplicate]

Are the experiments that prove that time dilation exists, actually proving that an atomic clocks ability to keep time is affected by gravity/acceleration? How do we know 100% that that is not the ...
0
votes
1answer
43 views

Time for a particle undergoing brownian motion to reach a point in a volume

I was wondering how one could calculate the average time a particle needs to reach a random point in a small sphere (filled by water) with a radius of maybe $10 \mu m$. I thought of using the ...
1
vote
1answer
27 views

Restrictions on Bell-type inequalities

While deriving and proving Bell-type inequalities of the form $|E(a,b)-E(a,b')|+|E(a',b)+E(a',b')|\leq 2$ I know that the conditions on the operators $O_a$ and $O_b$ are that they must be bounded ...
1
vote
0answers
46 views

Why doesn't the 1 dimensional ising model have a transition temperature?

Consider a 1 dimensional chain of spins that are able to either have the value $\sigma =$ $+1$, $-1$, from now on referred to as up and down. For the Hamiltonian $H = J \sum_{i,j} \sigma_i \sigma_j$ ...
3
votes
1answer
53 views

What are the definition and examples of topological excitation?

I read topological excitation in wiki, while it's too brief. What is the precise definition of topological excitation? And can give me some examples and explain why they are topological excitation? ...
1
vote
1answer
28 views

Fluid dynamics - immiscible liquids

Question: A U-tube of uniform cross-section is partially filled with a liquid I. Another liquid-II, which does not mix with liquid I is poured into one side. It is found that the liquid levels of the ...
1
vote
0answers
43 views

2 questions on 4-velocity

Firstly 4-velocity is defined by $u^\mu=\frac{dx^\mu}{d\tau}$ let us consider the component $x_i$ of $x^\mu$ then this derivative can be written as: ...
0
votes
0answers
16 views

Capacitor energy density and power density, units conversion [on hold]

I would like to know how to calculate the energy density and the power density for capacitor using these 2 equations: $$ E \left(\rm\frac{Wh}{Kg}\right) = \frac18 \frac{\rm C\left(\rm ...
0
votes
1answer
51 views

Why doesn't the electron lose or absorb energy while remaining in a selected orbit?

Postulate 2: When an electron revolves in any selected orbits, it neither emits nor absorbs energy . The energy of an electron in a particular orbit remains constant. Thus, Bohr, by postulating ...
2
votes
0answers
49 views

$E=mc^2$ what is unique about the speed of light? [duplicate]

What unique property of light, makes it the conversion factor between energy and mass? It has to be more than a coincidence that the speed of light, just happens to be the correct number number to ...
1
vote
0answers
23 views

Weight of a hemispherical bowl and a mass $m$ [on hold]

A particle of mass $m$ is A hemispherical bowl of mass M rests on a weighing scale. The inside surface of the bowl in frictionless. A particle of mass m is released from rest at the top of the bowl ...
28
votes
2answers
2k views

Why did “tickling the dragons tail” by Louis Slotin not cause an explosion?

I have been reading the excellent Command and Control by Eric Schlosser and discovered more about Louis Slotin's experiment with "tickling the dragons tail" and the infamous Demon Core. What I don't ...
13
votes
3answers
2k views

What does this depiction of a black hole in the movie Interstellar mean?

I was expecting a whirlpool in 3D and the matter glowing from friction as it nears the center, as I expected a event horizon to be negligible visually. How does this depiction work? How big is the ...
0
votes
0answers
47 views

$E=mc^2$ is incomplete? [duplicate]

So I was going through youtube and I found out these: http://www.youtube.com/watch?v=mkiCPMjpysc http://www.youtube.com/watch?v=NnMIhxWRGNw Can anyone here explain to me (with derivation if ...
7
votes
1answer
563 views

Why can we inflate the balloon?

I have an elementary question: I know from experiences that human can inflate (or fill with water) the standard ballon or latex medical glove. But I know also that in rubber/latex there are a pores. ...
0
votes
2answers
90 views

Is the Fundamental Theorem of Calculus really applicable to the definition of work?

When the force $F$ on an object is not constant, then the work it performs is defined as $$W = \int_{x_0}^{x} F(X)dX.$$ Now, the Fundamental Theorem of Calculus states that $$\text{If}\,\,\, f(x) ...
0
votes
4answers
749 views

Newton's third law.. please explain here

According to Newton's third law, the force acting on object is equal and opposite to the other object that is applying the force. If I push a table with 5N force then table is doing the same. But the ...
0
votes
0answers
36 views

Is time dilation a mechanical slowdown only? [duplicate]

I've recently read about the time dilation occurs at very high speeds. But I'm really wondering if it is just a mechanical slowdown of the clock only? What if we use clocks that does not use moving ...
1
vote
2answers
69 views

Are black holes “Immortal”?

Black holes are stars that are so massive, that when they die, they become so dense that not even light can escape. That means that a black hole is costantly adding mass and energy and thus making its ...
2
votes
2answers
33 views

Rare earth minerals in solarcell production

When I was looking at photovoltaic solar cell production I saw that there was some difficulty with rare earth minerals used in the production but i can't find which rare earth minerals. I have tried ...
3
votes
1answer
44 views

Could fish in plastic bags filled with water float like that?

I saw this gif earlier and it bothered me how the plastic water bags with fish in it are not submerged in water like they would if we don't do anything special with the water inside and outside the ...
-3
votes
0answers
10 views

Complete the formula that relates standard volumetric flow (Qstd) with Actual volumetric flow(Qact), knowing ρact and ρstd [on hold]

Complete the formula that relates standard volumetric flow (Qstd) with Actual volumetric flow(Qact), knowing ρact and ρstd. this is a question i must complete in my online instrumentation course ...
0
votes
0answers
13 views

Air unit selection and duct sizing [on hold]

I am not sure if this is the right place to post this. But would you please provide me with a concrete example showing the selection of an air heating/cooling unit along with the required duct sizing ...
0
votes
1answer
28 views

When an aircraft flies over, glass window vibrates…Infrasound?

When an aircraft flies over, my big glass window vibrates, making a ticktack beating. Its frequency sounds low, less than 10 beats per second actually. I'm wondering about the mechanism of this ...
0
votes
0answers
16 views

Quantum harmonic oscillator doughnut shape

When phase-space trajectory is plotted for classical harmonic oscillator for p(t)=mx0ωcos(ωt +δ0), a circle is obtained. When done same for the quantum harmonic oscillator, why do we get a doughnut ...
2
votes
2answers
69 views

How to handle the potential $V(x)$ or $V(\phi)$ which is not analytic in QM and QFT

In QM, $$\hat{x}\phi(p)=i\frac{\partial}{\partial p} \phi(p)$$ and when $V(x)$ is an analytic function of $x$, then $$V(\hat{x})\phi(p)=V(i\frac{\partial}{\partial p} )\phi(p)$$ and we can do Taylor ...
0
votes
0answers
10 views

Calculate the distance travelled by hot air before it looses its momentum

Hot air is released from a nozzle with certain velocity into the atmosphere. As the stream travels, it looses momentum and after some time mixes with air.How can we calculate the distance the stream ...
3
votes
0answers
14 views

Question about energy moving through one object to another

I think this question is part physics, and maybe part chemistry. I'm making electronic drums. On the top of the drum there's a flat surface (the drum head) you hit with a stick anywhere on the head. ...
2
votes
1answer
33 views

Superior attachment of Möbius strip

In this DIY project, the Möbius strip is used to make a spill-proof coffee cup carrier. The author uses a Möbius strip as the handle of this carrier and says If you attach a Möbius strip to an ...
0
votes
1answer
23 views

Problems with calculating Strontium-90 leakage due to Fukushima accident

Not long ago there was a spill of radioactive water at the Fukushima plants. Here are the data: $230 \times 10^6 \,\,\mathrm{Bq}$ of beta radiation are found in a liter of water. $t_{1/2} = 28.79 ...
1
vote
1answer
49 views

Is jumping the result of normal force or action-reaction?

Just a clarification question based on an example I read about. Can normal force do work on an object? The answer is yes, with an example being a person jumping. The normal force causes work to ...
0
votes
0answers
28 views

How to derive a new form of Hamiltonian operator in quantum mechanics using canonical commutation relation?

How does one derive $$\hat{H} = \frac{1}{2}\hat{p}^2m(\hat{q}) - \frac{i}{2}\hat{p}\frac{m'(\hat{q})}{m^2(\hat{q})} + V(\hat{q})$$ from hamiltonian $$\hat{H} = \hat{p}\frac{1}{2m(\hat{q})}\hat{p} + ...
0
votes
1answer
14 views

Why an undoped heterojunction causes potential barrier?

In this image (source) a potential double-barrier was created using GaAs and AlAs lattices (undoped). Why would any potential barrier be formed, if all the bonds are electrostatically balanced (i.e. ...
0
votes
1answer
37 views

What are the boundary conditions for EM waves normally incident on the interface between two dielectric media?

An EM wave, amplitude $E_0$, frequency $\omega_0$, is incident upon a material with relative permittivity (dielectric function) $$\varepsilon \left( z \right) = \left\{ \begin{gathered}{\varepsilon ...
0
votes
0answers
13 views

Tight binding method -kittel [on hold]

Actually my study on tight binding method from Solid state physics- Kittel is in totall mess. There are couple of points I would like myself to clarify on -How $\boldsymbol{<\phi_{m}|\phi_{j}>}$ ...
1
vote
0answers
8 views

Bell vs. diaphragm of stethoscope for low frequency sounds

Why is the bell of the stethoscope used to hear lower frequencies if it has a smaller diameter than the diaphragm? I would have thought that a bigger diameter diaphragm could pick up lower frequency ...

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