1. The problem statement, all variables and given/known data Two point charges q1=1[itex]\mu[/itex]C and q2=-1[itex]\mu[/itex]C with mass 1g each are at distance 1m from each other. The charges are released from rest at . Find the time t in seconds at which they collide. 2. Relevant equations F=kQ1*Q2/r^2. 3. The attempt at a solution Let the dist. of separation be r and the mass of charged be m. I think they will meet at the middle of separation.Force on q1=kq^2/r^2 so the acceleration =kq^2/r^2*m.But in this case acceleration is not constant.So I have to use calculus here. Let the charge q1 be at origin and at a distance x from origin acceleration=kq^2/(r-2x)^2*m( 'r-2x' because if q1 will move x meter towards q2 then q2 will also move x metre towards q1 so the length of separation will decrease by 2x) . For a small displacement dx this acceleration is constant.I tried to use S=ut+at^2/2.But I am unable to find u.Please help.