I just read that Centrifugal Force is a false force. It does not exist. Inertia (which is not a force) is mistakenly called Centrifugal force. Now, here is my question According to Newton's 3rd law of motion, forces always exist in pairs; action and reaction. Centripetal force which is the force acting on the body pushing it towards the center must have a pair that is the force acting on the object that is exerting the centripetal force. For example: a yo-yo twirled around a finger is pulled along the string by the finger towards the finger - centripetal force. The force with which the yo-yo pulls on the finger along the string What is that force called then? This has nothing to do with the inertia of the yo-yo which will make it fly along a straight line as soon as the centripetal force is moved.