Two bodies initially at rest, started moving towards each other due to mutual attraction. Which of the following is incorrect ?

Two particles A and B (both initially at rest ) start moving towards each other under a mutual force of attraction. At the instant when the speed of A is v and the speed of B is 2v, the speed of the centre of mass is

10 Two particles of masses m_(1) and m_(2) initially at rest start moving towards each other under their mutual force of attraction. The speed of the centre of mass at any time t, when they are at a distance r apart, is

10 Two particles of masses m_(1) and m_(2) initially at rest start moving towards each other under their mutual force of attraction. The speed of the centre of mass at any time t, when they are at a distance r apart, is

Two particle A and B (both initially at rest) start moving towards each other under 3 mutual force of attraction. At the instant when the speed of a is v and the speed of B is 2v, the speed of the centre of mass is

Two particles A and B, initially at rest, moves towards each other under a mutual force of attraction. At the instant when the speed of A is v and the speed of B is 2 v, the speed of centre of mass is

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