Question

explain example in walking on the ground , of conservation of momentum

Answer 1

The reaction force is what makes you move because it acts on you. Newton's Third Law of Motion explains that forces always come in action-reaction pairs. The Third Law states that for every action force, there is an equal and opposite reaction force. Imagine hitting a baseball.

Answer 2

when no external force acts on two interacting objects their total momentum remains constant it dosent change
as no other force acts rather then force applied by our body and the gravitational force and hence the momentum remains constant