Four objects roll without slipping down an identical incline from the same height: **solid sphere, solid cylinder, hollow sphere, hoop**. Order in which they reach the bottom (fastest first):

$a = g\sin\theta/(1 + k^2/R^2)$. Lower $k^2/R^2$ ⇒ faster. Values: solid sphere $2/5 = 0.40$; solid cyl $1/2 = 0.50$; hollow sphere $2/3 ≈ 0.67$; hoop $1$. So order of $a$: solid sphere > solid cyl > hollow sphere > hoop.