Q.

A ball of mass 0.15 kg is dropped from a height 10 m, strikes the ground and rebounds to the same height. The magnitude of impulse imparted to the ball is (g=10m/s2) nearly           [2021]
 

1 1.4 kg m/s  
2 0 kg m/s  
3 4.2 kg m/s  
4 2.1 kg m/s  

Ans.

(3)

Mass, m=0.15kg; h1=10m, h2=10m; g=10m/s2

The velocity at the time of strike when going downwards.

             v=-2gh1

and when moving up v'=2gh2

Impulse = change in momentum mv'-mv=2mv (As h1=h2)

=2×0.15×2×10×10=4.2kg m/s