Answer:

Newton's third law: If an object A exerts a force on object B, then object B must exert a force of equal magnitude and opposite direction back on object A.

1. The player's hand exerts a force on the ball (action). The ball exerts an equal and opposite force on the player's hand (reaction).

2. The hammer pushing the nail (action). The nail pushing the hammer back (reaction).

3. When the skater is pushing on the ground (action), the ground pushes back on his/her foot (reaction).

4. When a ball on one end of the cradle is pulled away from the others and then released, it strikes the next ball in the cradle, which remains motionless. But the ball on the opposite end of the row is thrown into the air, then swings back to strike the other balls, starting the chain reaction again in reverse.

Newton's Cradle aptly demonstrates the principle of the conservation of momentum . This principle states that when two objects collide, the total momentum of the objects before the collision is equal to the total momentum of the objects after the collision.

In other words, when the first ball of Newton's Cradle collides with the second, the first ball stops, but its momentum isn't lost, just transferred to the second ball, then the third, then the fourth, until it reaches the very last ball.