1. The problem statement, all variables and given/known data A horizontal disc of diameter 10 cm is spinning freely about a vertical axis through its centre at an angular speed of 80 revolutions per minute. A piece of putty of mass 7.0 g drops on to and sticks to the disc a distance of 3.0 cm from the centre. The angular speed reduces to 65 revolutions per minute. Calculate the moment of inertia of the disc. 2. Relevant equations I= MR2 3. The attempt at a solution R= 0.03 M= 0.007 but if i use the formula I= MR2,,,, what about the informaton they have given of rev/ min this is the angular speed.... not sure the method to do this???