For circular motion, the inward component of the net force causes centripetal acceleration.
The activity describes the quantity as the net inward force required for circular motion.
For uniform circular motion, the object moves with constant speed but changing direction. The acceleration points toward the center of the circle, so the inward component of the net force causes the motion.
In this simulation, the ball is attached to a string. The real force pulling the ball inward is the tension in the string.
There is no extra force called “centripetal force” added to the free-body diagram. The inward force comes from real forces such as tension, friction, gravity, or normal force, depending on the physical situation.