# All Questions

0answers
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### Size of upward force actin on the rocket! [on hold]

A 1500 kg rocket lifts off from the surface of the Moon by expelling exhaust from its lower end as shown. The force applied to the exhaust gas is 15 000 N downwards. Since the rocket is lifting off ...
0answers
50 views

4answers
1k views

### Intrinsic structure of electron

The electron contains finite negative charge.The same charges repel each other.What makes electron stable and why does it not burst? Is it a law of nature that the electron charge is the smallest ...
1answer
63 views

### Galilean Relativity is already included in Newton's Laws?

Usually I see an inertial reference frame being defined as a reference frame in which Newton's first and second laws holds. That means that if a particle is at rest, it stays at rest unless some ...
1answer
21 views

### First principle band structure calculation

In many literature, we see plots of the energy band structure from DFT simulation. How these eigen-energies are obtained as function of k within the DFT framework? Are they the physical quasiparticle ...
4answers
155 views

### Thermodynamics thought experiment

There is some ideal gas in a container moving with some velocity on a smooth surface and you suddenly stop it( say by using your hands) , will the temperature of the gas increase? It seems to me that ...
3answers
159 views

### Can the Unruh effect be confirmed by the LHC?

Two short questions regarding the Unruh effect. There are related answers on this forum and on wikipedia, but I am looking for confirmation of my own intuitive assumptions, so a straightfoward yes or ...
1answer
39 views

### Converting $F^2$ to $C^2$

I'm trying to convert Fahrenheit squared $F^2$ into Celsius squared $C^2$. I know how to convert a value $x$ in $F$ into $C$ with: $\frac{5}{9}(x - 32)$ I also know how to convert a value $x$ in ...
1answer
35 views

### Question about a car on a banked turn with no friction

A popular physics page explaining how a car can make a banked turn even with no friction : gives the following free body diagram and then says In the vertical direction there is no ...
1answer
127 views

### nuclear physics- Energetics and Mechanics of Nuclear Reaction Homework

A sample of $^{24}_{12}\mathrm{Mg}$ is bombarded by a monoenergetic proton. If the resulting nucleus in a $^{24}_{12}\mathrm{Mg}(p,\gamma)$ reaction; $^{24}_{12}\mathrm{Mg}(p,\gamma)$ has its ...
1answer
44 views

### In circular motion, what's preventing me from calculating the circumference of the circle, dividing it by time to find the speed of the object?

There are equations to solve for the speed in circular motion. However, is there anything preventing me from calculating the circumference from the given radius, and then divide that over the time to ...
1answer
63 views

### Could dark energy be what we think is spacetime?

I find it difficult to wrap my brain around how energy/matter, chemical reactions and resultant entropy or waste heat exist in abstract spacetime. First, how can a clock measure "time" without ...
0answers
36 views

### Fourier Transform and Canonical Transform

According to a book I'm reading, Fourier transform is a canonical transform. Anyone can prove that?
0answers
20 views

### What is the terminal velocity of a tungsten cylinder 20ft long and 2ft wide? (if it had a more aerodynamic end) [on hold]

I read somewhere that the drag coefficient of a sphere is 0.5. so I tried calculating with that and got 4150 MPH. I don't know if 1 would be a flat end or not. However I would assume if you were ...
7answers
2k views

### What exactly is heat?

Is it energy? Is it energy per unit volume? Is it energy per unit time i.e power? What is it?
1answer
71 views

### spinning a water bottle quickly

When we spin a water bottle so quickly, why don't the water inside the bottle come out ? It has to do with the normal force and the apparent weight , i think . but plz someone explain for me how does ...
2answers
55 views

### Using Maxwell's demon alongside quantum mechanics to contradict 2nd law of thermodynamics

Suppose we have a steady state universe with a gas chamber resembling that of Maxwell's demon that is used to power this hypothetical heat engine as molecules transfer to their respectable sides based ...
1answer
107 views

### I want to know why light even moves at all.

Never mind in a vacuum, why and how does light even move at all? What propels it?
1answer
24 views

### Are nuclear processes the only processes that release more energy than is input?

Are the nuclear processes of fission and fusion the only known processes or events that release more energy than is input to create those processes? I know I am being a little vague; I do not know the ...
1answer
31 views

### Tidal tails of galaxies after collision

When there is a collision of 2 disc shaped galaxies, there is a tail formation created from both the galaxies. I read here that this was due to tidal forces, but I couldn't figure out how this ...
0answers
31 views

### Translation of the Mechanique analytique [on hold]

Is there an English translation of the Mechanique analytique by Lagrange that is free? I have tried searching up online, however I only get French originals. The English translations seem all to be ...
1answer
41 views

### Electric field in a hollow object

I am currently visiting a course about electrodynamics. In my last lecture it was said that if a hollow sphere is inside of a bigger sphere, but only in the bigger sphere there are charges, the ...

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