For a spinning solid circular disk of radius a and constant thickness, the maximum stresses occur at the center of the disk and are given by:(3 ) 2a 2 4 t r s =s = +n rw where st is the tangential stress, sr is the radial stress, n is Poisson's ratio, w is the angular velocity, and r is the mass density. Show that maximum stored kinetic energy per unit mass of the disk is proportional to the specific strength. This
indicates that high specific strength materials like fiber composites make the most efficient flywheel materials.