[填空题]
A helicopter rotor blade can be considerebyq3+ ravl( boc,,tb rv q.*g-d a long thin rod, as sholv1(cxcabw j7;iss4s6 ku ::t wn in Fig. 8–46. 76a ivbxs:1c; cu:ks(wj 4slt (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? $m \cdot N$