4- A wheel is rotating about the fixed central axis with angular velocity (i = 20 rad/s. Its rotational inertia about the axis is, I = 2x10 kg m. Due to frictional torque the wheel slows down with angular deceleration, a = - 2.5 rad/s and stops, of = 0) (a) Find the time to stop for the wheel. What is the initial rotational kinetic energy of the wheel? (b) Find the magnitude of the frictional torque acting on the wheel. What is time rate of change of the angular momentum of the wheel? &