[填空题]
A grinding wheel is a8.gnqd -m r:qb una hu)ueg+ fy*xwib00 9iform cylinder with a radius of 8.50 cm and a mass of 0.580ba u0f i90x*+)gwhyue 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。 $m \cdot N$