You might have noticed that Newton’s second law of motion is somewhat more complex and abstract than the first law. You probably won’t be surprised to learn that Newton’s third law of motion is, in turn, more complicated than the second law.
According to Newton’s third law of motion, when one object exerts a force on a second object, the second object exerts a force on the first object of equal size, but in the opposite direction.
Watch the animation, which illustrates this law in the context of baseball. As you view it, keep in mind the relationships between forces and motion described by the first two laws of motion.
| Keyboard Shortcut | Action |
|---|---|
| Space | Pause/Play video playback |
| Enter | Pause/Play video playback |
| m | Mute/Unmute video volume |
| Up and Down arrows | Increase and decrease volume by 10% |
| Right and Left arrows | Seek forward or backward by 5 seconds |
| 0-9 | Fast seek to x% of the video. |
| f | Enter or exit fullscreen. (Note: To exit fullscreen in flash press the Esc key. |
| c | Press c to toggle captions on or off |
Pitcher (to Shortstop): Hey, man. [The two chest bump]
Manager: You two just acted out Newton’s third law. My work here is done.
Pitcher: We did?
Manager: Yeah, you two exerted equal forces on each other even though one of you is bigger than the other. And then the two of you went in opposite directions. See what I mean? Maybe not. Okay, let’s play it out.
[Pitcher pitches, Manager slams a line drive]
Manager: So what happened there?
Pitcher: Um, you hit a pretty good fastball.
Manager: Actually, the bat hit the ball. And the ball hit the bat. They hit each other, with equal, opposite force. Take a look.
Manager: See, the ball is object one, and the bat is object two. Object one pushes here against object two, so the ball bends the bat… And object two pushes against object one, with equal force. So the bat bends the ball.
Pitcher: Actually, the bat crushed the ball.
Manager: Bend or crush, the point is that the force of the bat on the ball is the same, or equal to, the force of the ball on the bat.
Pitcher: The force the bat exerts on the ball, is equal to the force the ball exerts on the bat. And those forces cause the ball and the bat to go in opposite directions.
Manager: Now you get it.
Pitcher: Whenever one object exerts a force on a second object, the second object exerts a force of equal size, but in the opposite direction, on the first object.
Write one or two sentence in which you apply Newton’s third law to another sport, such as soccer, football, or hockey. Alternatively, you can apply the law to another real-life situation, such as sitting down in a chair or stubbing your toe.