5.1 Rotational Kinematics

Rigid Systems

Up to Unit 4, we considered objects as point particles—idealized bodies with no shape or size. However, in Units 5 and 6, we expand to rigid systems (or rigid bodies), which possess defined shapes.

A rigid system is a model of a solid object in which the distances between any two points remain constant. In other words, a rigid body does not deform or change shape under ordinary forces.

This allows us to study rotational motion—how extended bodies rotate about fixed axes—alongside linear motion.