The homogeneous circular disk shown in Figure A3.4 has mass moment of inertia about its centre of mass of l = 3 kgm. It rotates about a fixed shaft at its centre and is attached to a torsional spring with constant k = 20 Nm/rad. At t = 0, the angle is = 0, the angular velocity is d /dt = 4 rad/s, and the disk is subjected to an oscillatory couple M(t)= 10 sin 2t Nm. Determine as a function of time.. Figure A3.4 M(1)