# All Questions

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### Anomalous calculation about stellar collision

Suppose two bodies of mass 'm',one of them is fixed and the another is free to move,they are separated by a distance 'l' initially and the system is at rest.What would be the speed of the free body if ...
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### If our planet had more gravitational force would rain clouds still form? If so, would they form at the same elevation, higher or lower?

If the acceleration of gravity on earth were greater would rain clouds still form? If so, would they form at a lower, higher or the same elevation? My question actually is related to a curiosity about ...
14 views

### Rindler's criterion and definition of linearity of the Lorentz and Poincaré transformations

In Wolfgang Rindler's "Introduction to Special Relativity", 2.ed. 1991, on p.11 his derivation of the special Lorentz transformation $x'=f(x)$ starts with the proposition that this ...
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### Water waves transverse

When waves arise from a point in water, they form circles around the point and it is referred to as a transverse wave. Is this because the x and y components are trigonometric graphs and so a graph of ...
248 views

### Finding constraints on acceleration if two objects' positions are related non-linearly

I'm taking a a first-quarter mechanics class at a university and we're currently covering Newton's laws of motion. The problems themselves are pretty similar to what I did in high school, but it seems ...
1 vote
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### Electromagnetic tensor in a FRW metric

In some papers [like https://arxiv.org/pdf/2204.06883.pdf, eq. (31) ], I see that the Electromagnetic tensor field, for a FRW metric (written in a conformal way) \begin{equation} ds^{2} = a^{2}(\tau) \...
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### Understanding where equation $2.3$ comes from?

I'm trying to understand this paper (equation $2.3$ specifically): Bini, D., Carini, P., & Jantzen, R. T. ($1995$). Relative observer kinematics in general relativity. Classical and Quantum ...
1 vote
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### Intrinsic parity

When we apply parity on a field two times, we demand that we should get back the same field. This gives us, $P^{2} =1$, which implies, $P \psi = e^{i \theta} \psi$ . This extra phase factor is ...
1 vote
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### Octopus Ride how much +G force in upward Jerk?

This is a version of the Octopus Ride here: https://www.youtube.com/watch?v=8flmhIAKTvQ They call it Hip Hop but really it is what you call it in other places, I felt my left Butt Cheek or Thigh cramp ...
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### Does the direction of angular momentum of a table fan different for two people standing behind the fan and in front of the fan?

Does angular momentum of a table fan depend on place of observation? What is its direction of angular momentum of a fan when I stand behind a table fan? In front of a table fan? And along the same ...
245 views

### Does a form of energy exist without any medium?

Does the Sun contain fire? Or some pure form of energy? If space has no air how can fire exist there? It may exist cause a burning piece of magnesium keeps on burning in vacuum but, to start fire, ...
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### How does this cyclist accelerate without expending energy?

https://youtu.be/2QBcc87yoc8 I came across this cyclist video on YouTube. Cyclist here is seen accelerating without peddling or expending energy into the system. How is it possible? Assuming air ...
1 vote
156 views

### How can we create suction, without the use of a vacuum?

How is it possible to create suction without the use of a vacuum? For example: As I understand, positive displacement pumps transport fluid by creating a vacuum at their inlet to draw in a distinct ...
I'm trying to better understand how information is quantified in the case of a closed system containing a single (fundamental) particle located at position $\vec{r}$ and traveling with a velocity \$\...