Chapter 9, Problem 7P

A pair of forces with equal magnitudes, opposite directions, and different lines of action is called a “couple.” When a couple acts on a rigid object, the couple produces a torque that does not depend on the location of the axis. The drawing shows a couple acting on a tire wrench, each force being perpendicular to the wrench. Determine an expression for the torque produced by the couple when the axis is perpendicular to the tire and passes through (a) point $A$ , (b) point $B$ , and (c) point $C$ . Express your answers in terms of the magnitude $F$ of the force and the length $L$ of the wrench.