the mass moment of inertia -> how hard it is to change the spin of an object.
Its not the shape that matters when spinning, its the mass that matters. If the mass is closer to the center of gravity it will spin easier because the mass isn't moving very much.
mass moment of inertia is a 2nd rank tensor. vector is rank 1 and a scalar is rank 0. We express as a 3x3 matrix.
Bunch of formula for normal objects.
moment of inertia = matrix * angular access