Various objects roll without slipping down an incline of vertical height H, all starting from rest at the same moment. The objects are a thin hoop, a spherical marble, a solid cylinder, and an empty soup can. In what order do they reach the bottom of the incline? The sliding box wins. For each we can state MgH=1/2Mv^2+1/2Icm w^2. The hoop has the largest moment of inertia; hence lowest speed and will arrive at the bottom behind the solid cylinder, which in turn will be behind the marble sphere. The empty can has most of its mass concentrated at R; therefore it will be a bit faster than the pure hoop but slower than the solid cylinder. Determine what will be the speed of a solid disk?