Introduction

1.1 Introduction

Circular motion is an everyday phenomenon — every revolving or rotating rigid object around us performs it. The chapter builds the dynamics of such motion and then generalises it to the rotation of extended rigid bodies.

The textbook draws one distinction here, and the board can ask for it directly.

• Revolution: every particle of the object describes a circle about some point outside the object, or about some other object. Example: the Earth revolving around the Sun.
• Rotation: the motion is about an axis of rotation that passes through the object itself. Example: the Earth spinning about its polar axis.

The rest of the chapter proceeds in two halves: sections 1.2 to 1.4 treat a particle in circular motion (kinematics, centripetal and centrifugal force, and the standard applications), and sections 1.5 to 1.11 build the rotational analogues of mass, momentum, force and kinetic energy for a rigid body.