[填空题]
A helicopter rotor blade can bi(l xjs:,sifp8w9s0w4xgd 2je considered a fh(*p*u6f zsm+mlea 3tn q*+23gh uurlong thin rod, as shown in Fig. 8–46m6hs*ha* ef3pt2+umn+g( qlruu* 3fz. (a) If each of the three rotor helicopter blades is 3.75 m long and has a mass of 160 kg, calculate the moment of inertia of the three rotor blades about the axis of rotation. $kg \cdot m^2$ (b) How much torque must the motor apply to bring the blades up to a speed of 5 $rev/s$ in 8.0 s? $m \cdot N$