Moment and Couple

In general, moment is the action of a force about a point which causes rotation. To compute moment about a point, one measures the distance between the point and the force by drawing a straight line from the point perpendicular to the force or its extension. Moment is defined as the force times distance:

M is usually measured in k-ft or lb-ft. Moment has either a clockwise or counter-clockwise direction.

Concept of Moment

Moment can always be resolved into a couple. Couple is the action of two equal and parallel forces which try to rotate the object. When we turn on or off a faucet we use a couple. To compute the forces in a couple, we divide the moment by the distance.

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