[填空题]
A hollow cylinder (hoop) is rolling on a horizontal surface at speed v=3lb5s 7d(unn 0ie ;i/m:nb)ide 6y0i g9/sklmu.3 $m/s$ when it reaches a 15 $^{\circ} $ incline. (a) How far up the incline will it go? $\approx$ m (round to one decimal place) (b) How long will it be on the incline before it arrives back at the bottom? s