A point charge `+q` is fixed at point `A` on the circumference of a fixed smooth non-conducting circular wire track of radius `R` in a gravity free space. A small ring of mass `m` and charge + which can slide freely on the wire track is given tangential velocity at point `B` which is diametrically opposite to `A`. If the distance of closest approach between the fixed charge and the ring is `R` then force applied by the wire track on the ring just after the release will be