A cockroach of mass m lies on the rim of a uniform disk of mass 4.29m that can rotate freely about its center like a merry-go-round. Initially the cockroach and disk rotate together with an angular velocity of 0.271 rad/s. Then the cockroach walks halfway to the center of the disk. (a) What then is the angular velocity of the cockroach-disk system? (b) What is the ratio K/K0 of the new kinetic energy of the system to its initial kinetic energy? I am not even sure how to begin this problem. I thought you could set up a ratio using v= r times omega. But that didn't work out, so I'm not sure where to even begin, even though the book says it relates to angular momentum.