The department of defense is testing out a new weapon which fires out a spinning ring (see the “chakram” from the Indian subcontinent). The rings that this weapon fires are approximately 20cm in inner diameter and 30cm in outer diameter and have a mass of 300 g. When fired, they rotate at 3000 revolutions per minute (about the axis of symmetry) and travel at a speed of 300 m/s. (a) What is the moment of inertia of the ring? Hint: Additivity of moment of inertia can be rewritten as subtractivity. Consider the ring as a solid disk minus a smaller solid disk!
(b) What is the kinetic energy of the disk after it has been launched?