Action-reaction pairs act on:

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. A key characteristic of these force pairs is that they result from the interaction between two distinct objects. 1. **Mechanism:** If object $A$ exerts a force $\vec{F}_{AB}$ on object $B$ (the action), then object $B$ simultaneously exerts a force $\vec{F}_{BA}$ on object $A$ (the reaction). 2. **Vector Form:** This is expressed as $\vec{F}_{AB} = -\vec{F}_{BA}$. 3. **Application:** Because the action force is applied to object $B$ and the reaction force is applied to object $A$, the forces act on **different bodies**. This is precisely why action-reaction pairs do not cancel each other out on a single object's free-body diagram.