# transfer formula for moment of inertia

## 819 Inverted T-section | Moment of Inertia

## 818 Hollow square section | Moment of Inertia and Radius of Gyration

**Problem 818**

A hollow square cross section consists of an 8 in. by 8 in. square from which is subtracted a concentrically placed square 4 in. by 4 in. Find the polar moment of inertia and the polar radius of gyration with respect to a z axis passing through one of the outside corners.

## Moment of Inertia and Radius of Gyration

**Moment of Inertia**

Moment of inertia, also called the second moment of area, is the product of area and the square of its moment arm about a reference axis.

Moment of inertia about the x-axis:

$\displaystyle I_x = \int y^2 \, dA$