[Jeff]

nm golfer

I agree 100% with what you state about the circle of an ellipse.

I drew those yellow lines because so many people think that the clubhead swingarc is circular, and they also believe that the body's swing center is the center of that circular clubhead arc.

You wrote-: "The centripetal force always points in the direction normal (perpendicular) to the path at any instant towards the instantaneous center of curvature. That location would rarely if ever be a golfer's body part (left shoulder... spine etc....) Its a location in space determined solely by the path of the object."

Exactly! That's the point that I have been making all this time.

You also wrote-: "Also... as the words "centripetal force requirement" imply, its something that is required to keep an object rotating but not something that does work (force through distance = work) or stores energy."

I think that centripetal force must do some work if it changes the direction of movement of an object (traveling at a constant speed) from a straight line path to a circular path. Force is surely needed to centripetally accelerate the object so that it moves more centrally (towards that instantaneous center of curvacture) while it is traveling at a constant speed.

I agree that CP force cannot store energy - the CP energy is in constant use if the object continues to travel along a circular path (if it is constantly being centripetally accelerated).

Jeff.