2
votes
1answer
720 views

Is energy always proportional to frequency?

Google has no results found for "energy not proportional to frequency" and many results for E=hf. Is there an example of an energy that is not proportional to frequency?
5
votes
7answers
1k views

Quantum computers: are they possible or impossible?

I know quantum computers are very complicated and my question is is there any way in "Principle" to create one? Are there already quantum computers being created?
1
vote
1answer
50 views

What creates the differences between the two channels of a stereophonic signal?

Given two identical microphones arranged in an ideal XY pattern, recording a single sound source at equal distance from both capsules, the two signals obtained are equal in amplitude, perfectly in ...
0
votes
2answers
23k views

Calculating force of impact

Since $\text{force = mass}\times\text{acceleration}$, is it right to say that an object traveling at a high constant velocity (zero acceleration), exerts zero force upon impact with a stationary ...
2
votes
1answer
661 views

Flow in parallel paths after pressure regulator

Consider the following: ...
23
votes
13answers
66k views

I don't understand what we really mean by voltage drop

This post is my best effort to seek assistance on a topic which is quite vague to me, so that I am struggling to formulate my questions. I hope that someone will be able to figure out what it is I'm ...
3
votes
1answer
145 views

Is this the correct way to I combine multiple interdependant pressure readings?

I want to measure the density in different layers of a suspension. To do this I want to place pressure sensors at different heights. Let's assume that the sensors are not by orders of magnitude more ...
1
vote
1answer
148 views

Thermodynamics and electromagnetic fields

The energy density in an electromagnetic field is given by: $u = (1/2) <\vec{E}^2 + \vec{B}^2>$ where $<,>$ denotes the average over time. In a cavity it holds that $u= u(T) = ...
4
votes
4answers
980 views

Wheel locks and spinout

Imagine driving in a straight line on a ice lake, when you hit the brakes, if your goal is to stay in straight path with no spinout, which wheels would you choose to have locked: front or rear? ...
1
vote
2answers
359 views

Motion of a pendulum

The equations of motions for a simple pendulum is given by $$\ddot{\theta} ~=~ -\frac{g}{\ell}\sin(\theta),$$ where $g$ is acceleration due to gravity and $\ell$ is the length of the pendulum's ...
3
votes
1answer
1k views

Differences of behaviour of a particle in a box in quantum theory between that in classic physics

Can anyone help me enlist 3 major differences between the quantum and classical physics of the behaviour of a particle in a box? I would like some insight into the differences without solving PDEs ...
-2
votes
3answers
764 views

A man running on the treadmill

Imagine a man is running on a treadmill. His inertia with respect to floor will be zero because he is not moving with respect to floor. If both he and the tread mill suddenly stops he will not fall, ...
2
votes
0answers
197 views

Phase transition through Molecular Dynamics Studies

I am doing non-equilibrium molecular dynamics to see the phase transition of single crystal metals in extreme condition (shock compression). I am using NVE to conserve total energy, every thing going ...
2
votes
2answers
204 views

A universe of angular momentum?

I read this on Wikipedia: [...] That most tangible way of expressing the essence of quantum mechanics is that we live in a universe of quantized angular momentum and the Planck constant is the ...
2
votes
1answer
168 views

Newtonian Gravity on a Riemannian $3$-Manifold

To solve the Poisson equation for the Newton Potential, say $\phi$, one can use the divergence theorem, such that $$\int_U \nabla^2 \phi \sqrt{g}~ dV= \int_{\partial U} <\nabla \phi,n> ...
1
vote
0answers
219 views

Is there any way to prove/disprove we are in a computer simulation? [closed]

Is there any way to prove/disprove we are in a computer simulation in some transcendental reality? Even if we are "really" not in a simulation, can we ever prove so? Even if some messages/evidence ...
2
votes
1answer
129 views

The number of mean free paths which a particle traverses is independent of the material traversed

This is a manual from a Monte Carlo physics manual: Computing the occurrence of a process Can anyone tell me why the number of mean free paths of a particle is independent of the material which it ...
1
vote
0answers
200 views

How much money does an unused but plugged-in cellphone-charger waste in a year, if its not getting warm?

Is it right as xkcd states: You can use heat flow to come up with simple rule of thumb: If an unused charger isn’t warm to the touch, it’s using less than a penny of electricity a day. Or, more ...
2
votes
1answer
2k views

Significance of the the Lagrange multipliers in statistical mechanics

In classic thermodynamics one can derive the Maxwell Boltzmann statistics by solving a Lagrange multipliers equation. In this process a new parameter $\beta$ is introduced to take account of the total ...
3
votes
1answer
225 views

A Book about the Bohr-Einstein debate?

A book about the Bohr-Einstein debate? Is there any book that details the correspondence between the two? The only books I could find are popular science books, I wonder if there is a book that lists ...
3
votes
1answer
601 views

Newton's third law of motion: An apple resting on the surface of earth

My friend asked me a question which was: For an apple resting on the floor, what is the action and reaction force pair? I said that the Earth exerts a gravitational force on the apple and the ...
4
votes
2answers
3k views

What is the optimal weight for a golf ball?

I am 32 now, and have forgotten the basic physics formulas we used in school. I am sitting with a question that is bugging me. If I had to hit two golf balls of different weight with the same force, ...
12
votes
3answers
474 views

Radio-dating and the age of the earth

I understand there are a few radio-dating methods to determine the age of the earth, uranium-lead to name one (maybe not the best though). The ratio Pb206 + Pb207 to U allows you to find when the ...
1
vote
1answer
994 views

Electric field strength between 2 positive charges [closed]

I'm having a lot of trouble trying to solve this problem: Three identical point charges of magnitude $+1.0$ $mC$ are located at the corners of a square that is $1.0$ $m$ on a side. A point charge of ...
2
votes
1answer
175 views

Holograms? Sci Fi or future fact?

Based on how light behaves when it passes through mediums, i.e. the wavelength of light changes when it passes through mediums of different refractive indexes, wouldn't it be possible to convert ...
5
votes
2answers
16k views

Capacitor circuits with light bulb

Let's say we have a normal circuit with a light bulb, with wires and a battery. When one places a capacitor in this circuit, how is the light bulb able to light up, even when the capacitor prevents ...
2
votes
3answers
1k views

Why the temperature is getting lower when the universe is expanding

As we know, if an ideal gas expands in vacuum, as its energy is unchanged, the temperature remains the same. An ideal gas's energy does not depend on volume. In general, the energy is $kT$ times the ...
2
votes
1answer
182 views

Reaction coordinate as a function of atomic positions

I'm going over some (molecular dynamics) related literature - specifically the derivation of the Weighted Histogram Analysis Method (WHAM). As a quick backdrop WHAM is a method for stitching ...
1
vote
1answer
192 views

Spacelike slicing of Schwarzschild geometry

I am having trouble understanding how to obtain a spacelike slicing of the Schwarchild black hole. I understand there is not a globally well defined timelike killing vector, so we can define t=cte ...
9
votes
3answers
2k views

Can something travel faster than light if it has always been travelling faster than light?

I know there are zillions of questions about faster than light travel, but please hear me out. According to special relativity, it is impossible to accelerate something to the speed of light. However, ...
0
votes
1answer
618 views

Is the total pressure coefficient always 1 in incompressible flow?

I have to do some calculations to get the drag from an experiment with a wake rake. In the equation I have to enter the total pressure coefficient $C_{pt}$, but in my calculations it seems to always ...
8
votes
1answer
3k views

Constants of motion vs. integrals of motion

Since the equation of mechanics are of second order in time, we know that for $N$ degrees of freedom we have to specify $2N$ initial conditions. One of them is the initial time $t_0$ and the rest of ...
2
votes
4answers
1k views

How Uncertainty Principle, Vacuum fluctuations and Energy Conservation coexist in QFT?

Recently I had a debate about the uncertainty principle in QFT that made me even more confused.. Because we use Fourier transforms in QFT, we should have an analogue to the usual Heisenberg ...
4
votes
2answers
2k views

If you had two “perfectly” flat surfaces of the same material?

Let's say you had 2 nano-engineered surfaces of diamond which were as 'flat' as possible (of course considering the radii of each carbon atom in the lattice)... would there be any friction between ...
1
vote
1answer
482 views

Different versions of Planck's law [duplicate]

For a presentation in physics I am going to talk about black body radiation since our book just mentions Planck's law, Wien's displacement law and Stefan-Boltzmann's law. I want to derive Wien's law ...
-1
votes
2answers
2k views

Electric potential energy and speed

If we have electric field and we put electron there , the electron will move in the opposite direction as the electric field. My question is electron in that direction will speed up or slows down ? ...
5
votes
3answers
365 views

Does a ball thrown in the air really stop at its apex, and if it does, wouldn't that violate the uncertainty principle?

When throwing a ball straight up, most experts say that it momentarily comes to a stop at its apex before its return fall. If it stops, wouldn't we know its velocity and position and wouldn't this ...
0
votes
0answers
85 views

Water Stream from a Horizontal Surface

If water was projected from a flat surface where gravity was equal all over the surface. What would happen when the water fell in on itself? The water is in a continuous stream and is perfectly ...
2
votes
1answer
344 views

Sound of packing tape dispensation?

I am sitting in a cigar lounge, and under the jazz music playing I can hear this strange, rising and falling tone, that sounds similar to one of those weird tubes you can find at a fun fair. You tilt ...
3
votes
3answers
1k views

Relation between the determinants of metric tensors

Recently I have started to study the classical theory of gravity. In Landau, Classical Theory of Field, paragraph 84 ("Distances and time intervals") , it is written We also state that the ...
56
votes
3answers
2k views

What causes insects to cast large shadows from where their feet are?

I recently stumbled upon this interesting image of a wasp, floating on water: Assuming this isn't photoshopped, I have a couple of questions: Why do you see its image like that (what's the ...
8
votes
1answer
2k views

Do glass panes become thicker at the bottom over time?

Is it true that a glass window, that has been placed in a wall for about 10 years or more, is thicker on the bottom than on the top? I can vaguely remember my physics teacher saying that this was ...
2
votes
1answer
2k views

Wave propagation in an incompressible flow

Incompressible approximation of fluid flow is usually known to be lame in modeling the propagation of any disturbance in it, predicting a speed equal to infinity for the propagation of the ...
8
votes
3answers
11k views

Is imagining 10 dimension video by Rob Bryanton has any invalid/wrong information? [closed]

I just watched this youtube video by Rob Bryanton and am wondering that is there anything invalid/wrong in term of real physics. I search for Rob Bryanton and it look like he has not-so-good ...
1
vote
1answer
105 views

Query about Bernoulli's principle

We know that the lower atmosphere has high pressure and as we go up, the pressure decreases, if it's so then why doesn't all gases fly up into the upper atmosphere from the lower following Bernoulli's ...
0
votes
2answers
126 views

Observing visible light itself by our eyes

We know that for any object to be seen by a human eye, the light from any source must be reflected from that object so that it reaches our eye and we can detect it.....but how do we see light itself? ...
0
votes
1answer
128 views

Explanation for the next steps of lamb-chaplygin dipole

Can someone explain me the steps please (I mean steps 2 and 3)? I didn't understand it. 1) Any flow field represented by a stream function $\psi$(x,r), defined as: v = - $\frac{\partial ...
3
votes
2answers
264 views

Can string theory be used to solve basic quantum problems?

When I studied physics I was shown that special relativity would become Newton's laws at low speeds. Similarly, quantum mechanics could also be shown to be Newtonian at large quantum numbers. My ...
2
votes
2answers
14k views

Calculating Average Velocity

I understand that the concept of an average of a data list means finding a certain value 'x', which ensures that the sum of the deviations of the numbers on the left of 'x' and on the right of 'x' ...
6
votes
1answer
413 views

Database of scattering amplitudes

I want to check whether my result for the invariant amplitude of the electron-electron scattering (to lowest order in $\alpha$; t+u channels) is correct or not. I can't find any reference that has ...

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