2. kr" potential Consider two bodies which orbit one another under the influence of the potential U(r) = krn where k and n are real constants such that kn > 0 and is the relative separation. a) What does the condition kn > 0 tell us about the force? b) Determine the effective potential Ueff (r) which describes motion about the center of mass. c) Sketch Ueff (r) for the cases of n = -3, -1, and 2. d) Within the effective one-dimensional description, determine the radius r = ro for which the particle (with given angular momentum l) can orbit at a fixed radius.