1. The problem statement, all variables and given/known data A horizontal disc of diameter 12.0 cm is spinning freely about a vertical axis through its centre at an angular speed of 72 revolutions per minute. A piece of putty of mass 5.0 g drops on to and sticks to the disc a distance of 4.0 cm from the centre. The angular speed reduces to 60 revolutions per minute. Calculate the moment of inertia of the disc. You should assume that no external torques are applied to the system during this process. 2. Relevant equations conservation of momentum I0w0=Ifwf parallel axis theorim Iw=Iw+mr^2 3. The attempt at a solution combining two equations gives Iw=Iw +mr^2 but do I need to convert angular speed to radians per sec? and I assume the mass is the putty mass not the disc?