[填空题]
A grinding wheel is a unft39591him3 5lt c g( vfrioxmifolxq. c hy23q1hg3t w2yrm cylinder with a radius of 8.50 cm and a mass of 0.58 w2yq3q3hxgc yt1.2lh 0 kg. Calculate (a) its moment of inertia about its center, $\approx$ $kg \cdot m^2$ (b) the applied torque needed to accelerate it from rest to 1500 rpm in 5.00 s if it is known to slow down from 1500 rpm to rest in 55.0 s。 $m \cdot N$