[填空题]
A 70-cm-diameter wheel rj1tlxj6tnk 4u- alt/8*wd. s accelerates uniformly abj97 , tc8biimlout its center from 130 rpm to 280 rpm in 4.0 s. Determic9jib7ltm 8 i,ne (a) its angular acceleration,$\approx$ $rad/s^2$(Round to one decimal places) (b) the radial and tangential components of the linear acceleration of a point on the edge of the wheel 2.0 s after it has started accelerating. $a_R$ $m/s^2$ $a_{tan}$ $m/s^2$