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.


  • 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.

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