Two bodies, A and B initially, at rest, move towards each other under mutual force of attraction. At the instant when the speed of A is v and that of B is 2v, the speed of the centre of mass of the bodies is:

Question

Two bodies, A and B initially, at rest, move towards each other under mutual force of attraction. At the instant when the speed of A is v and that of B is 2v, the speed of the centre of mass of the bodies is: (A) 3v (B) 2v (C) 1.5 v (D) v

Tardigrade Admin · Accepted Answer

When the sum of the external forces acting on a system vanishes, the velocity of the centre of mass of the system remains constant. In this case the two bodies move under mutual force of attraction, hence speed of centre of mass of the bodies is zero.

Q. Two bodies, A and B initially, at rest, move towards each other under mutual force of attraction. At the instant when the speed of A is v and that of B is 2v, the speed of the centre of mass of the bodies is:

3v

2v

1.5 v

v

zero

When the sum of the external forces acting on a system vanishes, the velocity of the centre of mass of the system remains constant. In this case the two bodies move under mutual force of attraction, hence speed of centre of mass of the bodies is zero.