Question

Two particles which are initially at rest, move towards each other under the action of their internal attraction. If their speeds are v and 2v at any instant, then the speed of centre of mass of the system will be

(a) 2v

(b) zero

(c) 1.5v

(d) v

Answer 1

Correct option (b) zero

Explanation:

As no external force is acting on the system, the centre of  mass must be rest i.e. v_CM = 0.