A girl pushes a merry go round until it is rotating with angular velocity of 1 rpm. The merry-go-round is a uniformly massive disc with mass M = 800 kg and a radius R = 2 m. The girl has mass m = 40 kg. (Treat the girl as a point mass)
(a) The girl jumps onto the edge of the merry-go-round. What is the angular velocity of the merry-go-round after she lands?
(b) The girl walks to the center of the merry go round. Does the kinetic energy or the angular momentum of the merry-go-round plus girl change? If so, by how much?