[填空题]
A hollow cylinder (hoop) is ro13s 3) pjuvbe 4 jm oq: g4b5lltygu7uw,*vfe2lling on a horizontal surface at speed v=3b,l ty. dlnc;)l :fp9v.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