A 0.2 kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30 m/s and rebounds up at 20 m/s. The magnitude of the impulse due to the collision with the sidewalk is:
A) 10 N .s
B) 6.0 N .s
C) 2.0 N .s
D) 19.6 N . s
E) 9.8 N .s

Question

Quizplus · Accepted Answer

Impulse is the change in momentum. The momentum of the ball before the collision is 0.2 kg * 30 m/s = 6 kg m/s. The momentum of the ball after the collision is 0.2 kg * 20 m/s = 4 kg m/s. The change in momentum is 6 kg m/s - 4 kg m/s = 2 kg m/s. The impulse is therefore 2 kg m/s.

A 02 Kg Rubber Ball Is Dropped from the Window of of a Building