Text: A torque is a concept which may be simply expressed as the effectiveness of a force in setting a body into rotation. 1. For a single particle with respect to a particular origin. This is expressed by the vector relation L = rxF, where L is the torque, r is the position vector relation respect to the origin, and F is the resultant force. The torque is equal to the time rate of change of the moment of momentum. 2. For a rigid body, the torque respect to a set of axes is expressed by the relation: L = vr x Fv dv where Fv is the resultant force per unit volume due to external forces on the element dv, and r is the position vector of the volume element. For a rigid body undergoing free rotation about a single axis, the torque L = l, where l is the moment of inertia and is the angular acceleration. 3. In engineering mechanics usage, a torque often refers to the torsional or twisting moment or couple which tends to twist a rigidly fixed object such as a shaft about an axis of rotation.

See Also:

Source: 100