Newton's third law review
|Action-reaction pair||The force exerted on an object is the action, and the force experienced by the object as a consequence of Newton’s third law is the reaction.|
Newton’s third law of motion
How to identify action-reaction pairs
Common mistakes and misconceptions
- People sometimes think force pairs cancel, resulting in no motion. The force pairs do not cancel, however, because they act on different systems. For example, a swimmer pushing off a pool wall (the action) exerts a force on the wall, and the wall also exerts a force (the reaction) on her. To figure out if she accelerates, we only consider the forces on her and then apply Newton’s second law. See the “How-to identify action-reaction pairs” section above for more details.
- People sometimes forget that Newton’s third law also applies to gravity. Just as the Earth pulls down on an object with a force , objects also pull on the Earth.