A simple real-life example of centripetal force is a rock tied to a string. When the string is swirled around, the tension in that string keeps the rock from flying off in a straight line.

With this definition, centripetal force would be real and centrifugal not real. Centripetal Force. Centripetal force is the force needed to make something move in a circle.

This force is the tension in the string (which is a real, fundamental force based on the electrostatic interactions between atoms). In this case, the tension would be the centripetal force ...