Question

A 0.5 kg ball moving with a speed of 12 m/s strikes a hard wall at an angle of 30° with the wall. It is reflected with the same speed and at the same angle. If the ball is in contact with the wall for 0.25 s, the average force acting on the wall is :

• A. 8 N
• B. 24 N
• C. 16 N
• D. 96 N

Answer 1

The Correct Option is B

To find the average force, you can use the impulse-momentum theorem. 
Impulse = Change in momentum. 
The ball is reflected with the same speed, so there is a change in momentum of 2 \(\times\) (0.5 kg \(\times\) 12 m/s) = 12 kg m/s. 
The time of contact is 0.25 s. 
Average force = \(\frac{\text{Impulse}} {\text{Time }}\)=\(\frac{ (12 kg m/s) }{ (0.25 s)}\) = 48 N. 
However, since the direction of the force changes, you might consider it as two equal and opposite impulses over time, resulting in an average force of 24 N in the direction of the wall.

Therefore, the correct option is (B): 24 N