Figure shows a rod of length L which is uniformly charged with linear charge density `lambda` kept on a smooth horizontal surface. Right end of rod in contact with a vertical fixed wall. A block of mass m and charge q is projected with a velocity v from a point very far from rod in the line of rod. find the distance of closest approach between the block & the left end A of the rod.

Answer

`r=L/((e^((2piin_(0) mv^(2))/(lambdaq))-1))`