|Additional Formula | Formula | Transfer of Axis
|The Radius of Gyration of an Area about a given axis is a distance k from the axis. At this distance k an equivalent area is thought of as a line Area parallel to the original axis. The moment of inertia of this Line Area about the original axis is unchanged.
|The Radius of Gyration of a Mass about a given axis is a distance k from the axis. At this distance k an equivalent mass is thought of as a Point Mass. The moment of inertia of this Point Mass about the original axis is unchanged.
|It is possible for two EQUAL areas to have equal MOMENT'S OF INERTIA about the same axis while having different dimensions.
|Figure 1 contains two rectangles. Setting the Area's and Moment's of Inertia equal, the following relationships can be found.
|h1 and b1 are constants.
|b2 depends on h2
In equ. (3) there is a limited range of h2 that yields a real solution.
d is maximized when h2 goes to zero.
This corresponds to an infinitely long, infinitely thin rectangle.
The maximum value of d is the Radius of Gyration.
|This is equivalent to using the general Radius of Gyration equation on a rectangle.
|The mass Radius of Gyration is the same concept just applied to a mass.