where T is resultant torque about the mass center, a is angular acceleration, and I is mass moment of inertia about an axis through the mass center.
Mass moment of inertia is referred to some axis of rotation, usually one through the CG. Refer again to Figure 10-1 which shows a mass of general shape and an xyz axis system. A differential element of mass is also shown. The mass moment of inertia of the differential element is equal to the product of its mass and the square of its distance from the axis of interest. With respect to the x, y, and z axes they are: