this means you can equate
1/2kq1q2/r^2 = 1/2mv^2
multiply your answer by two because there are two charges. you cannot multiply by two initially or it will mess up the algebra, multiply your answer.
oops x should be angle, right?
meaning:
MgLangle/2 = (ML^2/3)(d^2angle/dt^2)
(MgL/2)/(ML^2/3) = (d^2angle/dt^2)/angle
3g/2L = (d^2angle/dt^2)/angle
how do i isolate angle, then?