example of a couple

The moment of a couple is equal to one of the forces and the distances between the two. This hand is applying an equal force to each end of the top of a tap, producing a rotating effect about the central axis to turn it on and off. Both these forces are trying to turn the tap in the same direction, and together form a couple; the larger the tap-top, the larger the couple.

A couple is the application of two equal and opposite parallel forces applied to the same body that do not act in the same line. The forces create a torque, the moment of which is equal to the product of the force and the perpendicular distance between them. A couple can be balanced only by another equal or opposite couple if an equilibrium state is to be achieved.