Torque and Angular Momentum

When a net force acts on a body that is free to move, it simply produces linear motion in the direction of the force. But if the body is instead fixed to a point or an axis (a door on its hinges, a wheel on its axle, a nut being turned by a wrench), the very same kind of force instead produces rotation, and exactly how much rotational effect it has depends not only on the force's magnitude and direction but also on precisely where on the body it is applied, relative to the fixed point or axis. This turning ability of a force is called torque (or the moment of force). Everyday illustrations of torque are all around us: opening and closing a door about its hinges, or turning a nut with a wrench. …