Four idential charged spheres are located at the corners of a square with side length 2a. The spheres are much smaller than the size of the square (r<<a) and each sphere has a mass m and carries the same charge -Q.
a) What is the total electrostatic potential energy of the combined 4-sphere system when arranged as described?
b) How much kinetic energy does a sphere gain by moving very far away from the other three?
c) What is the speed of a sphere moved very far away?
The Attempt at a Solution
For part a, I think i got the right answer: Utot=k(4root2q^2+2q^2)/root2r
b)KE=1/2(4m)v^2 and thats it because thats all we know
c) I used Ui=Kf
and solve for v to get