Here's why:

* Inertia: Objects naturally move in a straight line unless acted upon by a force.

* Circular Motion: For an object to move in a circle, it needs a force constantly pulling it towards the center of the circle. This force is called the centripetal force.

* Examples:

* Swing: The tension in the rope acts as the centripetal force.

* Planet's orbit: The gravitational force between the planet and the sun acts as the centripetal force.

* Car turning: Friction between the tires and the road provides the centripetal force.

Important Note: Centripetal force is not a fundamental force like gravity or electromagnetism. It's a force that results from other forces acting on an object to keep it moving in a circular path.