According to newton's 3rd law, force exists in pair. When I attach a ball to a rope and rotate it, I am giving the ball an centripetal force to keep it moving in circular motion, so is the tension in the string the reaction force I am asking? I also want to ask about the reason why centrifugal force is considered as a pseudo-force. My explanation is that when you stand on the ball (imagine), you experience both the centripetal force (because you are rotating with the ball) and the centrifugal force (because you feel a force pushing you outward), but noting is actually providing the centrifugal force, and this also makes the rotating frame of reference an non-inertial frame. Is it correct? Thanks!