USMC PiCAT Practice Test

Centripetal force is the force that causes an object moving in a circular path to continually change direction, keeping it in that circular motion. The best illustration of centripetal force is a car turning at a high speed, as this scenario clearly demonstrates the need for a force directed toward the center of the circle along which the car is traveling. When a car makes a turn, the centripetal force acts to keep it following the curved path, counteracting the inertia that would otherwise cause it to move in a straight line.

In contrast, a bicycle coasting down a hill involves gravitational force acting on the bike and rider but does not illustrate circular motion or the centripetal force that keeps an object in a curved path. Similarly, an object falling to the ground is experiencing gravitational force, and a ball rolling on a flat surface is moving in a straight line without the circular motion necessary to exhibit centripetal force.