[填空题]
A helicopter rotor blade can be con2) j4+ p80/2 ej frayhymgfd7t:clc bpsidered a long thin rod, as shown in Fig. d9 9n d,p7gtioj69vrk 8–46djr 9kgnti,o97 9d 6vp. (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? $m \cdot N$