Two particles $A$ and $B$ initially at rest move towards each other under a mutual force of attraction. The speed of center of mass at the instant when the speed of $A$ is $v$ and the speed of $B$ is $2v$ is

Q. Two particles $A$ and $B$ initially at rest, move 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 center of mass of the system is

Q. 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 $B$ is $2v$, the speed of centre of mass is :

Q. 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

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

Q. Two particles $A$ and $B$ initially at rest, move towards each other, under mutual force of attraction. At an instance when the speed of $A$ is $v$ and speed of $B$ is $2v$, the speed of centre of mass (CM) is