4.1.4—The torque of a couple

For a couple, moment τ=F s, where F is the magnitude of either force and s is the perpendicular distance between their lines of action.

Use one force magnitude, not the sum of both forces. The couple moment is the same about any pivot because the net force is zero.

Increasing the handle separation from 0.10 m to 0.25 m at 12 N increases the turning moment from 1.2 to 3.0 N m.

Do not use the distance from a pivot to one force when the problem asks for a couple; use the force-line separation.