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
                                                                                                     12mv2=mghv=2gh=2x10x20v=20m/s in downward direction.
on striking the ground let the ball rebound with the velocity u in upward direction. it can be calculated as

                                                                                                     12mu2=mghu=2gh=2x10x5u=10m/s in upward direction

Change in momentum of the ball = final momentum of the ball -initial momentum of the ball
                                                    = mu-mvm( u +v)    as the direction of u and v are oppositeP=1(10+20) = 30kgm/s

  • 169

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).

  • 9
What are you looking for?