Question

Two particles a and b initially at rest moving towards each other under a mutual force of attraction. At the instant when the velocity of a is v and that of b is 2v the velocity of centre of mass of the system

Answer 1

As the two particles are moving towards each other, so the center of the mass will remain stationary and static and will not change. Thus the velocity of the center of mass will be zero due to no change in the center of the mass. 

Answer 2

Explanation:

Two particles a and b initially at rest moving towards each other under a mutual force of attraction. At the instant when the velocity of a is v and that of b is 2v the velocity of centre of mass of the system