a ball of mass m is dropped from a height h1 above one end of a uniform rod that pivots at its center. the rod has a mass m and length l. at the other end of the rod sits another ball of mass m, unattached to the rod. the dropped ball sticks to the rod after the collision. in terms of the given quantities, m, m, l, h1, what is the height h2 to which the other ball will go after the collision? assume that the rod is kept horizontal until the ball hits it.