A playground merry-go-round has a disk-shaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 210 kg and a radius of 1.8 m. A 35- kg child rides at the center of the merry-go-round while a playmate sets it turning at 0.10rpm. If the child then walks along a radius to the outer edge of the disk, how fast will the disk be turning (in rpm - but enter no unit)?

Answer 1

(.5*210*1.8^2)(.10)=(.5*210*1.8^2)+(35*1.8^2)(final rpm)

34.02=147.42*final rpm

34.02/147.42=final rpm

=.2308 rpm