When two objects interact, each exerts an equal-magnitude, opposite-direction force on the other. The pair consists of the same type of force acting on different objects. Balanced forces act on one object; a third-law pair cannot cancel directly in a force diagram for only one member of the interaction. Example: Describe a third-law force pair. Equal and opposite forces on different objects. A complete explanation links the relevant physical cause to its observable effect. Link cause and effect.