Mangetic and electric field, optics and escape velocity questions

[Leilaila]

http://img682.imageshack.us/i/77482562.jpg/"


I don't really understand these questions... Is there anyone who could tell me HOW to solve them? I don't ask about ONLY answers, I just want to understand how to solve these types of exercises.

The things I know:
1. the centrifugal force = the gravitational force
Fg=GmM/r^2
Fc=?

2. the potential =0 (+1 and -1)

5.
[PLAIN]http://img717.imageshack.us/img717/8140/96746786.png
and
[PLAIN]http://img806.imageshack.us/img806/4811/78862281.png
L>>|SM|, so r~12
sin ~ 0.007
so d*0.007= 1*633 d=...

ok but how many interference maxima can be observed?? is there an equation for that?

3. B inside = 0 because it's a sphere...
4 - I have no idea how to do this

 

[Cruikshank]

First, most of these are introductory physics; you might have better luck in that forum. (I'm new here myself.) Second, we're not supposed to give answers, just hints, so here:

1.Good so far, except it's centripetal, not centrifugal. Write F=ma and think carefully about each variable.
2.E is a vector. Add vectors by adding components.
3.Gauss's law helps here.
4.This one requires calculus. Look up the Biot-Savart law.
5.sin x can't get bigger than 1.

Good luck!