A charge particle 'q' is shot towards another charged particle 'Q' which is fixed, with a speed 'v'. It approaches 'Q' upto a closest distance r and then returns. If q were given a speed of '2v' the closest distance of approach would be

(a) r2 (b) 2r (c) r (d) r4

In the given process, the kinetic energy is converted into electric potential energy

For closest distance of r

1 / 2 m v² = k Qq / r, [ m is mass of the charged particle ]

For velocity 2v

K E = 1 / 2 m (2v) ²

= 1/2 m 4v²

4 x1/2 mv²

K E = 4 x k Qq / r

If R be new closest distance

K E = k Qq / R

4 x k Qq / r = k Qq / R

4 R = r