CIRCULAR MOTION
When a particle moves in a circular path with uniform speed, the direction of its velocity changes at every point on the circumference of the circle continuously. But the magnitude of the velocity remains constant. The change in the direction of velocity implies that there is some acceleration. It is directed towards the centre.
For the body to move on a circular path with constant speed the force applied on it should be such that it changes the direction of velocity but not its magnitude.
This is possible only if the force acts perpendicular to the direction of velocity at each and every point of its motion. Since the velocity is along the tangent, this force must be along the radius and towards the centre. This centre-seeking force is called centripetal force.