Written by the Fiveable Content Team โข Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 examโขWritten by the Fiveable Content Team โข Last updated September 2025
Definition
Newton's Third Law states that for every action, there is an equal and opposite reaction. This means that whenever one object exerts a force on another object, the second object exerts an equal but opposite force back on the first object.
Related terms
Force Pair: A force pair consists of two forces that are equal in magnitude but act in opposite directions on different objects. These pairs always occur together according to Newton's Third Law.
Momentum Conservation: Momentum conservation states that in a closed system where no external forces act, the total momentum before an event is equal to the total momentum after the event.
Action-Reaction Forces: Action-reaction forces are a pair of forces that occur simultaneously and act on two different objects. They have equal magnitudes but opposite directions.