7. A "merry-go-round" is a large horizontal platform for children to play on that can rotate freely. Imagine a certain merry-go-round has a radius of r = 3 m and a mass of 200 kg, and has been constructed out of fancy and well-lubricated bearings so that it rotates freely without friction. Suppose a child of mass 40 kg runs and jumps on the edge of the platform at 5 m/s; when they land on the edge, they are moving tangent to it. (See the diagram.) (a) Once the child jumps on the platform, how will it move? (b) Now, imagine that the child walks to the center of the platform. How will it be moving now