In Goldstein's 'Classical Mechanics' second edition at the top of page 30, the author directs the reader to page 102 of Osgood's 'Mechanics'. In the edition of Osgood that I looked at (I forgot to note which edition) on that page is the continuation of a discussion that begins on page 101 and concerns the misuse of the term 'centrifugal force' to describe circular motion. Osgood makes an impassioned argument (I think it was the passion that impressed Goldstein) but one that I think is incorrect. Please read the following carefully as there are two incorrect arguments here. There is the incorrect argument of the crank. Then there is the incorrect argument that Osgood makes against the crank. Crank: I agree that the particle on a string revolving around the central peg is subject to centripetal force, not centrifugal. However, I speak of the reactive force against the central peg. That force is centrifugal is it not? Osgood: There is a reactive force against the central peg, but it is not exerted by the particle. I don't understand what Osgood is driving at. The source of the reactive force is not the crank's issue, the mere existence of the force is. Here is a wiki article that, in my opinion, makes the same argument as the crank. http://en.wikipedia.org/wiki/Reactive_centrifugal_force" [Broken] I don't think the crank is correct, I don't think Osgood is correct, and I don't think the wiki page is correct. I think that the reactive force is centripetal. It points from the center of the peg to the center of the revolution of the revolving particle. Consider, for instance, the motion of a binary star system. One star is revolving about the other under the influence of a (somewhat) centripetal force. The reactive force on the other star is also centripetal and both stars revolve around a (somewhat) central point. Am I wrong? Edit: I googled osgood centrifugal and the first hit brought me to page 105 of Osgood's book and allowed me to page back to pages 101 and 102.