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comment Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy?
@Qmechanic: I understand why this question was closed there. I could have voted to close it myself as "homework without effort". Some one asked the poster: "What have you tried/ how do you plan to go about it?" However, in hindsight, this seems very funny, as it looks like this one-hundred-year-old problem was first solved only 5 years ago:-).
1h
answered Polarization of light for a fast moving observer
1h
answered Spin in Schrodingers Equations
4h
comment Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy?
Sorry, I misread your question.
4h
comment Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy?
I don't know what configuration of 5 points on a sphere would be more symmetric. By the way, what's the point of giving such assignments to students? As far as I understand, this problem was solved just recently.
5h
answered Where should five charges be placed inside a hollow sphere so as the system has the lowest potential energy?
Apr
13
comment Polarization of light upon reflection
@Ruslan: I wrote "are derived", not "were derived":-), as OP asked about "theoretical models".
Apr
13
answered Polarization of light upon reflection
Apr
10
answered What are pressure threshold patches called in professional terminology?
Apr
10
comment What is temperature?
@ACuriousMind: Actually, every physical system has translational degrees of freedom, the system you mention is just an idealization. No trap is rigid enough to totally eliminate the translational degrees of freedom. Iv4Ps' answer has two other problems though. The average kinetic energy is indeed directly related to the temperature of the object, but typically only if two additional conditions are met. First, the system must be classical (for example, the statement fails for a degenerate Fermi gas), second, the system must be close to a thermodynamic equilibrium.
Apr
9
answered How to measure the range of a horizontal projectile?
Apr
8
comment Charge present at the centroid of equilateral triangle
@Mixcels: because the charge's motion will be unstable with respect to displacements in the transverse direction, however small. There is a reason it is difficult, to say the least, to balance an egg on its narrow end.
Apr
8
comment Charge present at the centroid of equilateral triangle
@Mixcels: Imagine a ball "oscillating" on a saddle: its motion will be unstable with respect to ball motion orthogonal to its original trajectory, so the ball will eventually fall from the saddle. So the motion of your charge will be unstable with respect to its motion in the direction orthogonal to its displacement from the center of the triangle. So the charge will probably be driven outside of the triangle, and its motion will not be periodical.
Apr
7
answered Charge present at the centroid of equilateral triangle
Apr
7
answered A reliable aluminium battery that charges in a minute. What's the catch?
Apr
7
comment What's the difference between on-axis and peak intensity for a Gaussian beam?
@emc3636: That's right. You should put $\rho=0$, as you need "the ratio of the on axis intensity". And don't forget the $\omega 0/\omega$ factor.
Apr
6
answered What's the difference between on-axis and peak intensity for a Gaussian beam?
Apr
5
comment Electrical breakdown due to a charge
I would say the electric field is proportional to the inverse square of the distance?
Apr
5
comment How to find the force due to fluid pressure over a surface?
@Hritik Narayan: It looks like they measure $h$ from the bottom of the hemisphere, not as the height of the cylinder, as you do.
Apr
5
comment How to find the force due to fluid pressure over a surface?
@Hritik Narayan: Looks fine to me. Could you give the exact wording of the problem and "the answer you're supposed to get"?