4.1.2—The moment of a force

The moment (torque) about a pivot is τ=F d⊥, where d⊥ is the shortest perpendicular distance from the pivot to the force’s line of action.

Choose the pivot, resolve the turning sense, and use the perpendicular distance rather than the distance to the point where the force is applied.

A 20 N force acting 0.30 m perpendicularly from a hinge gives a 6.0 N m moment; a force through the hinge gives zero moment.

A large force can have a small moment if its line of action is close to the pivot; distance along the rod is not always d⊥.