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A ball of mass 0.15 kg hits the wall with its initial speed of 12 m s⁻¹ and bounces back without changing its initial speed. If the force applied by the wall on the ball during the contact is 100 N, calculate the time of contact of ball with the wall.

1. 0.018 s
2. 0.036 s
3. 0.009 s
4. 0.072 s

Correct answer: 0.036 s

Solution

The time of contact can be calculated using the impulse-momentum theorem, which states that the impulse (force multiplied by time) equals the change in momentum. Here, the change in momentum is twice the initial momentum of the ball (since it reverses direction), and dividing this by the force gives the time of contact.

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