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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 3v, the speed of centre of mass is:
A
2v
B
zero
C
v
D
4v
Detailed Solution
Since the only forces acting are internal (mutual attraction between A and B), the net external force on the system is zero. So the velocity of the centre of mass remains constant, equal to its initial value of zero (both particles initially at rest).