In this volume, we will learn about the third law of motion: law of action and reaction.

(1)Law of motion

3)Newton's third law --- sometimes referred to as the action-reaction law.

- If one object A exerts a force on another object B, then B simultaneously exerts a force on A. The two forces here are equal in size and opposite in direction.

- When a ship A pushes another ship B, the both ships will be pushed against each other by the same magnitude of force in the opposite direction.

- Since we usually take this kind of reaction for granted, you may have a hard time understanding the concept, but you can really feel the reaction force at a sudden start while riding in the vehicle with a large acceleration.

- The action of force that you are pushed back against your seat is the vehicle's reaction force toward the moving force.

- This reaction force is a required strength value for support structures of the drive mechanism.