[填空题]
A helicopter rotor blade can be 4gp 0ey7k2ljb--(,nupa sdhg/6ou wzconsidered a long thin rod, as/jk5n u hi7i; j( ak1nrq*l-ap shown in Fig. 8–46.(i7 hjr5jal*1inn ;uq/p ak- k (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? $m \cdot N$