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 duration of the contact of ball with the wall.

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(2) 0.036 s. Idea: the ball reverses direction at the same speed, so its momentum change is 2mv, and FΔ t=Δ p. Δ p=2mv=2×0.15×12=3.6 kg m s⁻¹. Δ t=(Δ p)/F=(3.6)/(100)=0.036 s. Sanity check: 36 ms is a realistic contact time for a ball on a hard wall, and a force of 100 N on a 150 g ball is about 68g of deceleration.

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 duration of the contact of ball with the wall.

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