# Area Moment of Inertia - Annulus Cross Section

## Description

The second moment of area, also known as moment of inertia of plane area, area moment of inertia, polar moment of area or second area moment, is a geometrical property of an area which reflects how its points are distributed with regard to an arbitrary axis.

The second moment of area for a shape is easier to be calculeted with respect to a parallel axis or with respect to a perpendicular axis through the centroid of the shape.

The formula calculates the moment of inertia of a filled annulus cross section with inner radius r1 and outer radius r2 with respect to a horizontal axis through the centroid of the annulus, parallel to the shape. (Parallel axis theorem)

## Variables

I_{x} | Area Moment of Inertia (mm^{4}) |

π | pi |

r2 | outer radius of annulus (mm) |

r1 | inner radius of annulus (mm) |