This illustrates the parallel Axis Theorem for a rectangular area. The Moment of Inertia ( Second Moment of Area ) of a rectangle about an axis parallel to the x axis is shown. The graph on the right shows how the moment varies with location of the axis.[br]The rectangle width (a) and height (b) as well as the location of the axis can be varied with the sliders.[br]The radius of Gyration, k[sub]x[/sub] , is also shown for the axis. As the axis moves further from the centroid what happens to the radius of gyration? A good way to visualize the radius of gyration is to place the rotation axis at y=0 (Axis=0). Then note the length of [math]k_{_{^x}}[/math] relative the y position of the centroid.