The moment of a force, also known as torque, is a measure of the turning effect or tendency of that force to cause an object to rotate about a specific point or axis (called the pivot or moment center). It quantifies how much a force causes rotation rather than just linear movement

Definition and Formula

• The moment of a force is calculated as the product of the magnitude of the force (F) and the perpendicular distance (d) from the pivot point to the line of action of the force:

Moment=F×d\text{Moment}=F\times dMoment=F×d

• The distance ddd is called the moment arm or lever arm and must be measured at a right angle to the force's direction

Key Points

• The larger the force or the greater the perpendicular distance from the pivot, the larger the moment.
• Moments can cause clockwise or counterclockwise rotation, which are often assigned positive or negative signs respectively for calculation purposes

• Moments are expressed in units such as newton-metres (Nm), foot-pounds, or other force-distance units

Example

If a force of 20 N is applied at a distance of 0.7 m from the pivot, the moment is:

M=20 N×0.7 m=14 NmM=20,\text{N}\times 0.7,\text{m}=14,\text{Nm}M=20N×0.7m=14Nm

This means the force creates a turning effect of 14 newton-metres about the pivot

Summary

The moment of a force is the rotational effect produced by a force applied at some distance from a pivot point. It is fundamental in understanding how levers, doors, wrenches, and many mechanical systems operate by converting forces into rotational motion