Angular Momentum

Jan 2009
In playground there is a small merry-go-round of radius 1.25m and mass 175kg. Assume the merry -go-round to be a uniform disc. A child of mass 45kg runs at a speed of 3.0 m/s tangent to the rim of the merry-go-round (initially at rest) and jumps on. If we neglect friction, what is the angular speed of the merry-go-round after the child has jumped on and is standing at its outer rim?

A) 0.82 rad/s
B) 2.4 rad/s
C) 0.49 rad/s
D) 1.2 rad/s
E) 0.41 rad/s