2.3 Newton’s Third Law of Motion

Newton’s third, and final, law of motion states that for each action, there is an equal and opposite reaction. For example, as a rocket expels hot gases during launch, the rocket is propelled upward. The gases, which are pushed toward the earth by the rocket, exert an equal (in magnitude) and opposite (in direction) force on the rocket, pushing it away from the earth. A similar situation occurs when a ball bounces on the ground. At the moment of impact, the ball exerts a force on the earth causing it to draw back slightly. Likewise, the earth exerts an equal and opposite force on the ball, causing it to bounce back up. (Note: the ball’s motion change is greater, as it has less mass, so its motion is affected more by an equal and oposite force).