1. The problem statement, all variables and given/known data A hollow cylinder (hoop) is rolling on a horizontal surface at speed v= 3.3 m/s when it reaches a 15 degree incline. (a) How far up the incline will it go? (b) How long will it be on the incline before it arrives back at the bottom? 2. Relevant equations Energy conservation: 1/2 Iw^2 + 1/2mv^2 = mgh v^2 = vo^2 +2ax x=vot + .5at^2 v=vo+at 3. The attempt at a solution I for this problem is (I think) 1/2 m (r1^2 + r2^2), but the r's cancel because w^2 = v^2/(r1^2 + r2^2) So I believe the energy equation simplifies to .25v^2 + .5v^2 = gh I solve and get h = .833 and so the length = .833/sin15 = 3.22 However, the book says the length is 4.29. Also, after that I don't know where to go. For time, I tried v=vo+at, for a I used 9.8sin 15 and t (up) I got 1.3s However, the total t= 5.2 s Thank you so much!