Question

A ball of mass 1 kg is dropped from height 9.8m strikes the ground and rebounds at a height of 4.9m if the time of contact between the ball and the ground is 0.1s .Find impulse and force

Answer 1

Velocity of the ball when it hit the ground can be calculated as 12mv2=mgh⇒v=2gh−−−√=2x10x20−−−−−−−√⇒v=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=mgh⇒u=2gh−−−√=2x10x5−−−−−−√⇒u=10m/s in upward directionChange in momentum of the ball = final momentum of the ball −initial momentum of the ball = mu⇀−mv⇀⇒m( u +v) as the direction of u and v are opposite∆P=1(10+20) =30kgm/s