Couple (mechanics)

In mechanics, a couple is a system of forces with a resultant (a.k.a. net or sum) moment of force but no resultant force.

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${\displaystyle {\textbf {F}}={\frac {d}{dt}}(m{\textbf {v}})}$ Second law of motion
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A more descriptive term is force couple or pure moment. Its effect is to impart angular momentum but no linear momentum. In rigid body dynamics, force couples are free vectors, meaning their effects on a body are independent of the point of application.

The resultant moment of a couple is a special case of moment. A couple has the property that it is independent of reference point.