In order to get a weight reduction, a 15 cm diameter solid steel shaft rotating at 150 rpm. The shaft is 3 meters long and the density of steel is 8.05 g/cm3. This shaft is replaced by a Titanium (p = 4.506 g/cm3) tube with a 15 cm OD and an 10 cm ID. Determine the reduction in kinetic energy in this system.