The table that follows lists four pairs of initial and final angular velocities for a rotating fan blade. The elapsed time for each of the four pairs of angular velocities is 4.0 s. For each of the four pairs, find the average angular acceleration (magnitude and direction as given by the algebraic sign of your answer).
Initial angular velocity v0 ____________________Final angular velocity w
(a) +2.0 rad/s ................................................... +5.0 rad/s
(b) +5.0 rad/s ................................................... +2.0 rad/s
(c) -7.0 rad/s ................................................... -3.0 rad/s
(d) +4.0 rad/s ................................................... -4.0 rad/s