58) A heavy car A of mass 2000 kg travelling at 10 m/s has a head-on collision with a sports car B of mass 500 kg. If both cars stop dead on colliding, what was the velocity of car B ?
Say, velocity of B before collision be V m/s
Initial momentum = 2000 x 10 + 500 x V kg m/s
Final momentum = 0
As per law of conservation of linear momentum:
20000 + 500 V =0
=> V = – 20000/500 = – 40 m/s
So velocity of car B was 40 m/s towards A.(they had head on collision)