Learning Introductory Physics with Activities

Since a rigid object undergoes both translational and rotational motion, it is important to be able to relate the various forces acting on an object to each kind of motion. This is done by creating an angular analogue of The Law of Motion.

The angular acceleration $\overrightarrow{\alpha }$ introduced in Section 11.5 is the angular analogue for the translational acceleration. The moment of inertia $I$ is the angular analogue for mass, which you will study in more detail in upcoming sections. The net torque is a direct analogue to the net force: you can find it by determining the vector sum of all torques acting on a system.