An open cylinder is dropped vertically and smoothly into the black groove on a spinning turntable. Then it is smoothly removed again. (a) How does the angular velocity of the table qualitatively change when you add the ring? When you remove the ring? (b) Is the angular momentum of the system conserved in both cases? If not, in which cases is it conserved and why? (c) Derive the formula for the change of angular velocity on landing.