12.10 The Vector Description of Rotational Motion

Rotation about a fixed axis, such as an axle, can be described in terms of a scalar angular velocity $\omega$ and a scalar torque $\tau$, using a plus or minus sign to indicate the direction of rotation. This is very much analogous to the one-dimensional kinematics of Chapter 2. For more general rotational motion, angular velocity, torque, and other quantities must be treated as vectors. We won’t go into much detail because the subject rapidly gets very complicated, but we will sketch some important basic ideas.