After reading (https://en.wikipedia.org/wiki/Reactive_centrifugal_force) (especially third paragraph of the introduction) and comparing it with the answer by Bob Jacobsen posted here (Why does a rotating non-rigid object elongate?), I cannot make the statements agree with each other. My question is:
Are the centripetal force and the reactive centrifugal force also present in the rotating frame? I would guess so as the rotating object needs to be hold in place (applies to any frame). But additionally, there is now this "fictitious" centrifugal force, which causes the elongation of non-rigid objects, right?