Newton's third law: action-reaction force pairs

Newton's third law says that whenever one object exerts a force on a second object, the second object exerts a force back on the first that is equal in size and opposite in direction. These two forces always act on different objects, which is why they do not cancel each other out. A rocket pushes exhaust gases backward, and the gases push the rocket forward; a swimmer pushes water backward, and the water pushes the swimmer forward. When a bug hits a car's windshield, the force on the bug and the force on the car are exactly equal, even though the effects are very different, because the bug has far less mass and so accelerates far more. Third-law pairs are shown by drawing a separate free body diagram for each object, with the two forces as equal-length arrows pointing in opposite directions, and an experiment with two force sensors pulling or pushing on each other shows both readings are always equal in size.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report