Question

A ball moving with a speed of 30 m/s hits the wall and bounces back with same speed. The contact time between the ball and the wall is 0.1 s. Calculate the force exerted by the wall on the ball if mass of the ball is 0.25kg.

• A. 0 N
• B. - 100N
• C. - 300N
• D. - 150N
• E. 100N

Answer 1

Answer: (D)

- 150N

Given : $v=30$ m/s $t=0.1$ s $m=0.25kg$

The ball bounces back with same speed after hitting the wall.

Thus change in its momentum $\Delta P=mv-(-mv)=2mv=2\times 0.25\times 30=15$ $kg.m/s$

Using $\Delta P=|F|t$

$\therefore$ $15=|F|\times 0.1$ $⟹|F|=150$ N

Thus the force exerted by the wall on the ball $F=-150$ N