Question

Why does a person hit harder when he falls on a concrete floor than when he falls on a heap of sand from the same height

Answer 1

A person hit harder when he falls on a concrete floor than when he falls on a heap of sand from the same height because on a hard surface he is brought to rest in a very short time, so greater force comes into action and he is hit harder. On the other hand, on a heap of sand, he is brought to rest in a longer time and so lesser force is called into play and he is hit slower.Since the sand has many different little sand pebbles and they move increasing your time of impact. When you hit a hard floor nothing is there to cushion you. You just hit a hard floor. Sand is supportive and increases your time of impact so you don't feel all the force on your body like you would if you hit a hard floor

It is based on the law of conservation of momentum that states that the sum of momentum of two objects before collision is equal to sum of momentum after the collision provided there is no external unbalanced force acting on them.