A uniform disk of radius 0.9 m and mass 3.2 kg is rotating about its center of mass. Its moment of inertia about its center of mass is I=1/2mR2. Its angular velocity as a function of time is given by ω(t)=3kt2/t13 where k = 5 rad and t1= 5 s. Find the magnitude of the net torque about the center of mass acting on the disk at t= 7 seconds.