Electric Potential Energy

Question

Charges A, B, and C each with charge +q are arranged in an equilateral triangle with length d.

If all the charges are let go and they fly off to infinity, what is the speed that each of the charges reach?

Answer 1

Potential energy = k_eq²/d² for two charges brought from infinity to d apart. Bringing the third d away from the other 2 results in a total energy of 3k_eq²/d² . Because of symmetry, each charge will end up having 1/3 of that energy at infinity as kinetic energy:

1/2 mv² = k_eq²/d² for each particle.