# Circular motion and rotation

The special types of motion we have considered so far – uniform motion and linear motion with constant acceleration – followed a linear path. Here we shall consider motion whose *path is curved*.

We speak of **circular motion** when a particle or the centre of mass of an extended object moves round in a circular path.

**Rotation** is when each point of an extended object moves round in different circular paths at different rates. There is a set of points in this type of motion that stay fixed: we call this set the **axis of rotation.** We say that the extended object rotates about this axis.

## Prerequisites

- the fundamental quantities of kinematics: position, displacement, velocity and acceleration;
- vectors v scalars;
- addition and subtraction of vectors;
- the scalar product (dot product) of vectors;
- the vector product (cross product) of vectors;
- the fundamentals of differential calculus (including integration).
- the concepts of work and energy;
- the work–kinetic energy theorem.

## Learning objectives

By the end of this course, students will be able to

- classify motion types;
- calculate the angular quantities for certain special types of circular motion and rotation;
- interpret the concepts of work and energy also for rotating objects;
- apply a fundamental conservation law to understand physical phenomena.