1. The problem statement, all variables and given/known data This is a problem I was thinking about which I haven't come across in my course. Two particles with mass, m, and a positive charge, q, are separated by a distance r0. One particle is unable to move while the other is released and is repelled. Find an equation for the motion of the particle. 2. Relevant equations F=q2/cr2 a=F/m 3. The attempt at a solution The problem I have in working out the acceleration at any time here is that r is a time dependent variable. Although this seems like a pretty important thing to know how to calculate I end up going around in circles with the maths.