# A ball of mass 1 kg is dropped from 20 m height on the ground and it rebounds to height 5 m . Find the magnitude of change in momentum duribg its collidion with the ground.Pls help experts.

Velocity of the ball when it hit the ground can be calculated as

on striking the ground let the ball rebound with the velocity u in upward direction. it can be calculated as

Change in momentum of the ball = final momentum of the ball $-$initial momentum of the ball
=

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V = (2gh)^1/2 =20 m/s downwards when it hits the ground

Since it rebounds to height 5m its velocity afterwards is =(2gh`)^1/2 =10 m/s upwards

So net change in momentum is 30 kgm/s.(positive direction is upwards).

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