Physics
posted by Beth .
Two disks are rotating about the same axis. Disk A has a moment of inertia of 4.53 kg·m2 and an angular velocity of +4.55 rad/s. Disk B is rotating with an angular velocity of 6.86 rad/s. The two disks are then linked together without the aid of any external torques, so that they rotate as a single unit with an angular velocity of 2.24 rad/s. The axis of rotation for this unit is the same as that for the separate disks. What is the moment of inertia of disk B?

Angular momentum is conserved.
Ia*wa + Ib*wb = (Ia + Ib)*wfinal
4.53*4.55  6.86*Ib = (4.53+Ib)*2.24
Solve for Ib.