# All Questions

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### Topological Phases? [on hold]

I am reading about topological phases in condense matter physics and I have been faced with this confusion  Matter transformed from some kind of fermions(electrons for example) to another kind of ...
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### Magnetic Lorentz force on a tube of conducting liquid [on hold]

A tube videos if conducting liquid on the horizontal plane placed in a perpendicular magnetic field B has a current density J upwards. Would the magnetic lorentz force contribute to pressure ...
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### Description of charged sphere with Heaviside function in cylindrical coordinates

I need to describe density of charge of uniformly charged sphere (radius R, total charge Q, position of centre (0,0,0)) with Dirac delta function and Heaviside step function. The hard part is to ...
141 views

### If the force of friction is 20 N for a moving body does acceleration increase with the increase of the mass?

A body is moving and the only force acting on it is the force of friction. If we put another body on this moving body somehow the force of friction will increase; does its acceleration change?
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### velocity vs Water? [on hold]

How can you balance and accelerate on water... What would we the equation be for that? How can a hoverboard stay on sea level on water?
233 views

### Proof of Bethe-Bloch stopping power

I want to prove the Bethe-Bloch stopping power formula but I don't know where to start. Any one can offer a book or paper? Related: http://en.wikipedia.org/wiki/Bethe_formula
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### What will limit the speed at which one can play the piano?

I thought about this as a fun question. Suppose we provide a piano player that is limited only by the typical relativistic rules (i.e., hands and fingers cannot move faster the speed of light), so ...
35 views

### Simple Momentum Problem (F=p/t) [on hold]

I cannot figure out this problem for the life of me: The answer should be 2400 N. We know that $F=\Delta p/ \Delta t$ (force equals change in momentum over change in time). The initial momentum is ...
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### How long does it take to a local perturbation to propagate along a quantum system?

Imagine to have a one-dimensional system in its ground state, and to apply a local perturbation at one edge of the system. How does the system evolve after being perturbed? More specifically, how ...