Rolling down on Incline

A rigid body with mass mm and radius rr will roll down on incline with linear acceleration aa along the incline

a=gsinθ1+I/mr2(1)\tag{1} a = \frac{g \sin\theta}{1 + I / mr^2}

where θ\theta is angle of the incline with horizontal direction and II is moment of inertia of the rigid body. Previous equation becomes

a=23gsinθ(2)\tag{2} a = \tfrac23 g \sin\theta

for a solid disk (I=12mr2I = \tfrac12 m r^2) and

a=57gsinθ(3)\tag{3} a = \tfrac57 g \sin\theta

for a solid sphere (I=25mr2I = \tfrac25 m r^2).