A horizontal disk of diameter 12.0cm 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 5.0g drops on to and sticks to the disk a distance of 4.0cm from the centre. The angular speed reduces to 60 revolutions per minute. 1. I need to calculate the moment of inertia of the disc. I can assume that no external torques are applied to the system during this process. 2. A constant tangential force is now applied to the rim of the disk which brings it to rest in 6.0s. Calculate the magnitude of this force. 3. Calculate the rotational energy of the system before and after the putty is added to the disc.