A fan has four blades attached to a central shaft. The blades arel_f=11cm long and each blade have a uniformly distributed mass ofm_f=0.16kg. The fan spins up from rest to an angular speed of_f= 111 rad/s int_f= 0.85 s.

Part (a)Treat each fan blade as a uniform rod of lengthl_frotating about its end. Enter an expression for the total change in the angular momentum Lof the fan during the spin up. Assume the angular momentum of the central shaft is insignificant.

L= (4/3)mflf2f Correct!

Part (b)Give an expression for the average torque_fthat the fan's motor exerts on the fan as it spins up.

= L/tf Correct!

PLEASE SOLVE Part (c)If the fan spins through 7.5 rotations during the spin up, calculate the workWin joules, that the fan's motor does on the fan.

W=