Question

Why does a person injure himself more if he jumps on a hard ground than a sand surface?

Answer 1

• In the case of jumping on sand, the feet penetrates deep into the sand so that it exerts less force on the sand. As a result, sand also exert less force only on the feet according to Newton's law.
• In the case of hard ground surface, the feet can't penetrate into the surface since the surface is rigid. So, the feet applies more force on the surface and as a result the hard ground surface also exert an equal amount of force which is large enough to hurt more on the feet.