Question

A ball of mass 0.45 kg is heading towards a wall with a speed of 25 m/sec. After hitting the wall the ball bounces back with a speed of 20 m/sec. The ball was in contact with the wall for 0.003 seconds. What is the average force the wall exerts on the ball?

• A. 760 N
• B. 3000 N
• C. 3750 N
• D. 6750 N

Answer 1

The correct option is D 6750 N

From impulse - momentum equation
$(\sum \overrightarrow{F})\times \Delta t=m(\overrightarrow{V_f}-\overrightarrow{V_0})$
Given, $\overrightarrow{V_0}=25m/sec,\overrightarrow{V_f}=-20m/sec$
$\Delta t=0.003\text{seconds}$
m = 0.45 kg
$F=\frac{0.45}{0.003}(-20-25)$
​​​​​​​$=6750N$