Question

A ball of mass `0.5kg` moving with a speed of `10m//s` rebounds after striking normally a perfectly elastic wall. Find the change in momentum of the ball . If contact time with the wall is `0.1s`, what force is exerted by wall?

Answer 1

Here, `m =0.5 kg, u=m//s v=10m//s, dt=0.1s, F=?`
Change in momentum of ball,
`dp=m(v-u)=0.5(-10-10)= -10kg m//s`
`F=(dp)/(dt)=(-10)/(0.1)= -100N`
Negative sign indicates that force is in a direction opposite to the initial direction of motion of the ball.