A box is pushed across a horizontal table at a constant speed. Of the forces acting, which pair do we know are equal in magnitude because of Newton's third law?
A) The normal force on the box and the weight of the box.
B) The normal force on the box and the normal force on the table from the box.
C) The force of kinetic friction on the box and the external pushing force applied to the box.
D) None of these are interaction pairs.

Question

Quizplus · Accepted Answer

According to Newton's third law, for every action, there is an equal and opposite reaction. Therefore, the normal force on the box and the normal force on the table from the box are equal in magnitude but opposite in direction, making them an interaction pair. The weight of the box is balanced by the normal force on the box, but they are not necessarily equal in magnitude. The force of kinetic friction and the external pushing force are not an interaction pair, as they act on different objects.

A Box Is Pushed Across a Horizontal Table at a Constant