1. The problem statement, all variables and given/known data The possible orbit of a particle moving around a black hole can be described using the effective potential UGR(r) (in effect, potential energy per unit mass): UGR(r) = -GM/r + l2/2m2r2 - Rsl2/2m2r3 where the symbols have their usual meaning and in particular Rs = 2GM / c2 is the Schwarzschild radius for the black hole. We then use the energy balance equation K = 1/2 mr2 + mUGR = constant to illustrate the main features of the possible orbits. (a) Show that the function UGR has a minimum and maximum value at r = r- and r = r+ respectively and determine expressions for these qualities. (b) Briefly describe the possible orbits. 2. Relevant equations Listed above 3. The attempt at a solution Please help.