Define circular motion and centripetal force.

Circular motion refers to the motion of an object that travels in a circular path. In a circular motion, the direction of the object's velocity is constantly changing, but its speed may or may not be constant. An example of circular motion is a car turning a corner, a planet orbiting around a star, or a ball whirling around on the end of a string.

Centripetal force, on the other hand, is the force that keeps an object moving in a circular path. It is always directed towards the centre of the circular path and is responsible for changing the direction of the object's velocity, but not its magnitude or speed. Centripetal force is provided by a physical force, such as tension in a string, gravity, or friction. Without centripetal force, an object in circular motion would continue moving in a straight line tangent to the circular path.