[填空题]
A helicopter rotor bl-y5ssh:c;e h9v xs +ha;u xnn4 :.er b-kaygg,,yq,qq ade can be considered a long thin rod, as shown in Fig. 8–4-4nqq gyyu e,rg,;:q k n.b,xa6. (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? $m \cdot N$