The mass moment of inertia, or simply moment of inertia, indicates the extent to which an object resists to change in angular velocity. As with a linear moving object, force is needed to bring about this change. This is a moment (of force) with a rotating object. We refer to the relationship between moment (of force) (M) and the resulting angular acceleration (α) as the moment of inertia (I) and is expressed in kilograms times square meters (kg.m2).

\( \vec{\ M} = I\cdot\vec{\ α}\)