PS7-3 A disc with a mass moment of inertia, /= 10 kg-m2 is mounted at the end of 1.0-meter-long solid square rod, 25 mm per side. The torsional natural frequency in rad/s is given by Wn = ' Im where formulas for k, are found in text or notes Determine the torsional natural frequency of the system for the rod for three different materials: (a) steel, (b) aluminum, and (c) copper.