A person jumps from a height on soft sand. Which one of the following is the correct reason for less likely injury to the person?
A.The sand exerts no reaction force.
B.The sand reduces the change in momentum.
C.The sand increases the impact time.✓ Correct
D.The sand increases the momentum.
Explanation
By the impulse–momentum theorem, F × Δt = Δp. The change in momentum of the person upon landing depends only on the landing velocity and is independent of the surface. Soft sand allows the person's body to decelerate over a longer time interval Δt, which by the relation F = Δp/Δt reduces the average force on the body and hence the risk of injury. The reaction force is not zero (it equals the person's deceleration force), and momentum change is the same as on a hard surface.
💡 Practice unlimited NDA PYQs + AI-tracked progress on each topic. Sign up free →