physics problem

65. A disk of radius R has an initial mass M. Then a hole of radius 1/4 R is drilled, with its edge at the disk center (Fig. 10.30). Fine the new rotational inertia about the central axis. Hint: Find the rotational inertia of the missing piece, and subtract it from that of the whole disk. You’ll need to determine what fraction the missing mass if of the total M and use the parallel-axis theorem.