[填空题]
A helicopter rotor blade can be considered a long thin rod,-v7ts aye+ j i cb*8pdi002aey as shog kclc(4yijxw9y h ,ja 146g2ewn in Fig. 8–4jy 9xw4h2 i1 c6 kg(agjec,y4l6. (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? $m \cdot N$