1.

A boy of mass 50kg is standing on a frictionless surface. He throws a ball of mass 2kg away from him with a speed of 10m/s. Find the final speed of the centre of mass.(a) 0m/s(b) 20m/s(c) 10m/s(d) 0.4m/sThe question was asked in exam.Question is from System of Particles topic in section System of Particles and Rotational Motion of Physics – Class 11

Answer»

Correct choice is (a) 0m/s

The best explanation: Initially the boy was at rest and there is no friction, so the net force on the ball-boy SYSTEM is zero.Hence, their momentum change will be zero and FINAL VELOCITY of centre will also be zero.Note that boy will move BACKWARDS with a speed of 2*10/50 = 0.4m/s.



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