Question

a point charge of q of mass m is placed at centre of a fixed ring of charge Q and radius R. what minimum velocity should be given to q so that it would reach far away from ring

Answer 1

As we know
U=1/2mv^2=KqQ/R

1/2mv^2=KqQ/R
mv^2=2KqQ/R
Therefore,
v =(2KqQ/Rm)^1/2

Answer 2

A point charge of q of mass m is placed at centre of a fixed ring of charge Q and radius R. Answer is attached , hopes it helps u.