A force can make an object turn about a fixed point called the pivot. The turning effect of a force about a pivot is called its moment. A bigger force gives a bigger moment, and so does applying the same force further from the pivot. That is why a door handle is fixed far from the hinges.
The moment is found with: moment (N m) = force (N) × distance (m). The distance is the perpendicular distance from the pivot to the line of the force, which means it is measured normal to the direction of the force. The unit is the newton metre, written N m. If the force is not at right angles to the bar, the distance normal to the force is shorter, so the moment is smaller.
Worked example: a force of 40 N pushes at right angles on a spanner 0.30 m from the nut. Moment = 40 × 0.30 = 12 N m. A longer spanner of 0.60 m gives the same moment with a force of only 20 N, because the distance is doubled and the force can be halved.