A playground merry-go-round of radius 2.00 m has a moment of inertia I = 325 kg·m2 and is rotating about a frictionless vertical axle. As a child of mass 25.0 kg stands at a distance of 1.00 m from the axle, the system (merry-go-round and child) rotates at the rate of 12.5 rev/min. The child then proceeds to walk toward the edge of the merry-go-round. What is the angular speed of the system when the child reaches the edge?

Question

anonymous · Answer

My work.  Please let me know what I did wrong.  I noticed I didn't actually use the given Inertia...

vincent-lyon.fr · Answer

Moment of inertia of the system is moment of inertia of the merry-go-round + moment of inertia of the child.
$I_{tot}=I+mr^2$  

$I$ will remain the same, but $r$ will change from 1m to 2m.