On the website http://www.real-world-physics-problems.com/physics-of-billiards.html
they take this equation ∑Mg = IG∝ where ∝ = -agx/r for the rotation of a rigid body where there is no slipping
They then change the equation to F⋅(h-r) = IG(-agx/r)
why is ∑MG = F⋅(h-r) when ∝= -agx/r?