Newton's Third Law of Motion
Newton's third law of motion
Newton's third law states that when one body exerts a force on the other body, the first body experiences a force that is equal in magnitude and opposite in direction of the exerted force.
When a ball bounces, it pushes the ground downward, so at the same time the ground pushes the ball upward.
When a bird flies, it pushes the air downward with its wings, so at the same time the air pushes the bird upward.
When you swim, you push the water backward with your hands (and sometimes also your feet), so at the same time the water pushes you forward.
When you walk, you push the ground backward with your shoes (and sometimes on your feet), so at the same time the ground pushes you forward.