Work Step by Step
The lever arm is the shortest distance between the applied force (i.e., the line along which the force acts) and the rotational axis. This is discussed on page 139, and examples are shown in Figures 8.19-8.20. If the line of action of the pushing force passes directly through the CM, there is zero lever arm about the CM. The magnitude of torque is the magnitude of force multiplied by the length of the lever arm (page 139). With zero lever arm, there is no torque.