Circular motion is a movement of an object along the circumference of a circle or rotation along a circular path or a circular orbit. The rotation around a fixed axis of a three-dimensional body involves circular motion of its parts but it is assumed as motion of a point mass in a plane. Hence the center of mass of a body is considered to undergo circular motion. It can be uniform, that is, with constant angular rate of rotation or non-uniform with a changing rate of rotation. Examples of circular motion: Satellite orbiting the Earth at constant altitude, a car turning through a curve in a race track, an electron moving perpendicular to a uniform magnetic field, and a gear turning inside a mechanism.

When a particle moves in a circle with constant speed, the motion is called uniform circular motion. A car moving at constant speed along a circular path, satellite moving in a circular orbit are examples of uniform circular motion. The direction of acceleration changes continuously so that it always point towards the center of the circle but the magnitude of acceleration remains same at all times.

At the top of the circle, the acceleration points down and at the bottom of the circle the acceleration points up. Such change in direction of velocity involves acceleration of the moving object by a centripetal force, which pulls the moving object towards the center of the circular orbit. A roller coaster car that slows down and speeds up as it moves around a vertical loop is an example of non-uniform circular motion in which the magnitude of acceleration also changes along with direction.