The rotor of an electric motor has rotational inertia Im = 2.5*10-3 kg · m2 about its central axis. The motor is used to change the orientation of the space probe in which it is mounted. The motor axis is mounted along the central axis of the probe. The probe has rotational inertia Ip = 8 kg · m2 about this axis. Calculate the number of revolutions of the rotor required to turn the probe through 30° about its axis. Not sure where to start, except that you have to use the idea of conservation of angular momentum.