Hi, I'm in the middle of programming an inertia system and am only really just starting to appreciate what the heck inertia is :) I have been taught inertia, but I haven't actually applied it in a real situation (all my exams and tutorials have resulted in formulae giving answers like 2/7Ma^2). So I've written a function to find inertia of a sphere and I've plugged some numbers in. I'm a bit confused over what formulae to use for starters. I can sorta see that inertia of the spheres centre might be useless? given that they're totally symetrical? Am I off with this? For inertia of a sphere about the diamater I'm using the equation 2/5 Ma^2. Is this appropriate? Also I've plugged in numbers (like I said). I've never got a numerical answer for a system before so I'd appreciate some guidance as to wether or not I'm correct. sphere at 0,0,0 radius 2 mass 1 rotation about point on diameter 2/5 Ma^2 0.4 * 1 * 4 MI = 1.6 ?