Let two charged particle be given some velocities and released on paths which are parallel and l distance away(perpendicular distance). Now at t=0 they are at very large distance away. So if they approach towards each other then find the closest approach distance. I could not solve it. So take your own variables and solve for general case.
What will happen when oppositely charged particles. I mean they will be attracted and then after joining of the particles what will happen?? I guess it will be an inelastic collision. But if u have some more thoughts share it.