A moment of inertia is one of the mass properties of a mechanism, describing its resistance to changes in rotational acceleration. The moment of inertia is expressed as the integral over the rigid body's volume of its density, multiplied by the square of the distance to the axis. The axis can be located at either the coordinate system origin or at the mechanism's center of gravity. The Inertia area of the Mass Properties dialog box has six values for the various possible moments of inertia.