Final answer:
The weight of a cup on a table and the table's normal force are not an action-reaction pair according to Newton's third law. The real pairs are the Earth and cup mutually attracting, and the table and cup pushing against each other with equal and opposite forces.
Step-by-step explanation:
The forces of the weight of a cup pushing down on the table and the table pushing back with a normal force are not an example of an action-reaction pair, because they act on the same system, which is the cup-table system. According to Newton's third law of motion, an action-reaction pair consists of forces that act on two different systems. In this scenario, the weight of the cup is the action of gravity on the cup, and the reaction to this force is an equal and opposite gravitational pull that the cup exerts on the Earth. Conversely, the normal force the table applies to the cup is balanced by an equal and opposite force that the cup exerts on the table, forming another action-reaction pair. Therefore, the real action-reaction pairs involved are: (1) the Earth pulling on the cup and the cup pulling on the Earth, and (2) the table pushing up on the cup and the cup pushing down on the table.