Centrifugal Force vs. Centripetal Force

We see it in the spin cycle of a washing machine or when children ride on a merry-go-round.
Centrifugal force is often confused with its counterpart, centripetal force, because they are so closely related. Centrifugal force is defined as the apparent force that is felt by an object moving in a curved path that acts outwardly away from the center of rotation. It is more inertia than a force. An example of centrifugal force is the earth's revolution around the sun. Another is passengers feeling pushed outward on a merry-go-round.
Centripetal force is defined as the force that is necessary to keep an object moving in a curved path and that is directed inward toward the center of rotation. If you are in a spacecraft orbiting the earth, the centripetal force is the force of gravity. Another example is spinning an object on a string. The tension on the rope pulls the object in toward the center.
Centripetal force and centrifugal force are the same force, just in opposite directions, because they are experienced from different frames of reference.

Centripetal force is an actual force; centrifugal force is an apparent force. In other words, when twirling a mass on a string, the string exerts an inward centripetal force on the mass, while mass appears to exert an outward centrifugal force on the string.