Mechanics, rotation, angular deceleration. Part 2

Solution Preview

initial rotaional speed
wo = 800 rpm = 800/60 rps = 2*pi*40/3 rad/s = 80*pi/3 rad/s
Final rotational speed,
wf = 0
time t = 6 s
angular acceleration alpha = ?
wf = wo + alpha*t
=> alpha = - ...