Question: A playground merry-go-round of radius R = 1.80 m has a moment of inertia I = 255 kg •m2 and is rotating at 8.0 rev/min about a frictionless vertical axle. Facing the axle, a 24.0-kg child hops onto the merry-go-round and manages to sit down on the edge.
Question 1: What is the new angular speed of the merry-go-round?
If possible just a brief explanation how you got the answer?