[填空题]
A helicopter rotor blade can y7eruai..(, (br fahl be considere30yx eeaiin+*qy+ s6 k(gkx0+t szg 5dd a long thin rod, as shown in Fig. 8–46 k* 5d+0n ex0kgxti3s yzy+ase(+g6qi. (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? $m \cdot N$