[填空题]
A helicopter rotor blade can 6mi tlla)l,(ppv tborj f tl:2i4q/:: be con iyl pm53+prry3j;a;t sidered a long thin rod, as shown in Fig. 8–46. y+rj3my;ir5l pp;3at (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? $m \cdot N$