An electric motor exerts a constant torque of 'r = 10 N - m on a average value at 200 W ' grindstone mounted on its shaft; the moment of inertia of the grindstone is I = 2.0 kg - m2 . It the system starts from rest, find the work done by the motor in 8.0 s and the kinetic energy at the v Part A - Practice Problem: end of this time. What was the average power delivered by the motor? Suppose we now turn off the motor and apply a brake to bring the grindstone from its greatest angular speed of 60 rad/s to a stop. If the brake gene constant torque of 30 N - m , find the total work done (including signs) needed to stop the grindstone. Express your answer in joules. W: J m mum Answer V Part B - Practice Problem: Find the average power (including signs) needed to stop the grindstone in Part A Express your answer in watts. .oon? P: W m Muest