All Questions
237,297
questions
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Why is Special Relativity preferred over Lorentz Ether Theory?
Special Relativity and Lorentz Ether Theory make the same predictions, so they cannot be experimentally differentiated. (Are Lorentz aether theory and special relativity fully equivalent?). As such, ...
- 1
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1
answer
22
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Braking distance vs. mass of the vehicle
We did an actual experiment where we checked braking distances of multiple trucks (rigid and semis), which had different GVW and consequently also axle loads. The results were very clear: for the same ...
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11
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Can Entropy be considered a kind of Affine Parameter?
In general relativity and differential geometry, an affine parameter is used to parameterize geodesics such that the geodesic equation $\nabla_{\mathbf{T}} \mathbf{T} = 0$ holds true, and the ...
- 2,039
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7
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How to calculating the induced charge on a spherical surface
I was trying to calculate the induced charge on a hemispherical surface of radius a with a point charge q at a distance b from the center using the method of images. However, the problem is that the ...
-2
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0
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18
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What is the meaning of velocity in Bohmian trajectories [closed]
Given a quantum particle of mass m with state $\psi=exp(ip_1 x/\hbar)+exp(ip_2 x/\hbar)$ all of their bohmian trajectories have constant velocity $(p_1+p_2)/2$ However from the point of view of ...
-4
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2
answers
33
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is a humans gravitational pull strong enough to attract germs and make us sick all the time
Since humans are so much bigger than bacteria , and large objects attract small objects , are we attracting bacteria and virus?
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19
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Dirac infers the form of a change in coordinates from the fact that $g_{\mu\nu}$ remains a function of $l_\sigma x^\sigma$ only ... how?
In Dirac's discussion of gravitational waves ("GTR", Chap. 33), he is working in the case where $g_{\mu\nu}$ are plane waves: waves moving in one direction only. In this case, $g_{\mu\nu}$ ...
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$F=ma$ and why it is accurate? [closed]
Why is $F=mv$ not a moot point? If an object has a set mass and one moves upon it with a set velocity, say the wind, then the set force, say gravity, acts upon it, the object never moves or it does at ...
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1
answer
43
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Why is $*F^{\mu \nu} *F_{\mu \nu}$ not considered in Lagrangian of EM?
In Lagrangian of electromagnetism $F_{\mu \nu} F^{\mu \nu}$ and $*F_{\mu \nu} F^{\mu \nu}$ are used, where the $*$ denotes Hodge dual. But $*F^{\mu \nu} *F_{\mu \nu}$ is not used, why?
I know an ...
- 43
2
votes
5
answers
48
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Clarification on Work-Energy Theorem
The professor derived the Work-Energy Theorem using the following steps:
$F=ma$
$Fd=mad$
$W=m(v^2−u^2)/2$
$W=\frac{1}{2}mv^2−\frac{1}{2}mu^2$
$W=ΔKE$
So, it seems that work only changes the kinetic ...
- 91
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15
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Why does $a\cos{\theta}$ represent rotation in the Kerr metric?
In any introductory book to GR where the Kerr metric is reviewed, they all apply transformations of the form:
$$cdu' = cdu + ia\cos\theta;\text{ } dr' = dr + ia\cos\theta$$
In the end, the result ...
- 505
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0
answers
14
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Correction Factor of Log Mean Temperature Difference
Background
In thermal equilibrium without phase change, the heat transfer $Q$ between two fluids with parallel flow or counter flow configuration is expressed as
\begin{align}
Q \; = \; U A \; ...
- 1,083
-1
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15
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A cylinder has two sides containing gas and water separately [closed]
A rectangular cuboid is made up of two identical cubes which have side length a = 10 cm. The cubes are separated by a frictionless piston of negligible mass in the middle. The cube on the left ...
-7
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0
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33
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Would quantum entanglement lead faster-than-light communication when collapse? [closed]
Assume there are a pair of AB particle in entangled state: |fin>=|00>+|11>
(where the first digit is the state of particle A and the second digit is the state of B particle)
Lets prepare 100 ...
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0
answers
15
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Physical Process Classification [closed]
Is there a comprehensive classification for physical methods or physical processes causing material size decreases
e.g.,
cutting processes - Shredding Crusher Grinding Granulating Pulverizing
...
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