Question

A playground merry-go-round of radius r = 2.20 m has a moment of inertia i = 240 kg · m2 and is rotating at 12.0 rev/min about a frictionless vertical axle. facing the axle, a 23.0-kg child hops onto the merry-go-round and manages to sit down on the edge. what is the new angular speed of the merry-go-round?

Answer 1

You can apply conservation of angular momentum since there is no external torque on the system. I have done that in the picture below. Remember to always convert to correct units. Just plug numbers in on what I’ve given you and you should get the final angular speed