# All Questions

3 views

### Is this the reason why acceleration is said absolute?

I've seem sometimes people saying that although uniform motion on a straight line cannot be detected and hence it is not absolute, acceleration is indeed absolute in Classical Mechanics (I don't know ...
8 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 ...
3 views

### Form of the S matrix for interacting sclar field

The solution for the equation $S^{-1} c_k^{in} S = c_k^{in} + f_ k$ is S= $exp(f_k^{*}c_k^{in} - f_kc_k^{in*})$. Here $c_k^{in}$ is an operator and $f_k$ is a c number. This is the equation for ...
3 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 ...
5 views

### Is density functional theory a mean-field theory?

Is density functional theory exact or just a mean-field theory?
6 views

### Fourier Transform and Canonical Transform

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

### Is there any evidence that the theory of everything exists?

I was reading a book and they were talking about Terra Australis. Terra Australis is a hypothetical continent first posited in Antiquity and which appeared on maps between the 15th and 18th ...
13 views

### Force and lions

Alright. So me and some other people right now need an answer to this. If you have 1 trillion lions traveling at 81 kilometers (top speed of a lion) towards the Sun in a pretty dense ball. (As dense a ...
15 views

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

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 ...
17 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 ...
13 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 ...
11 views

### Behaviour of a degenerate classical harmonic oscillator

Solving the partition function for a system of N non-interacting particles with energy levels given by $E_{j} = j \epsilon$ and degeneracy g, $g_{j} = j$, and assuming the particles are ...
23 views

### Translation of the Mechanique analytique

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 ...
20 views

18 views

### Combination of current sources

Most books say that to connect sources in series, the current sources will be equal in magnitude. I really don't understand the meaning of this statement. What happens if you connect current sources ...
27 views

### In the Leidenfrost effect why dropplets of water can travel uphill?

The Leidenfrost effect is a phenomenon in which a liquid, in near contact with a mass significantly hotter than the liquid's boiling point, produces an insulating vapor layer keeping that liquid from ...
1k views

### Why doesn't light affect a compass?

In our daily life a lot of photons of visible light, infrared and radio etc move around us. We know that light is an electromagnetic radiation. So why doesn't that electromagnetic radiation affect a ...