# Recangular Prism: Moment Of Inertia

1. Jan 27, 2005

### pyrexyn

There is a rectangular prism (L x W x H) = (72 x 36 x 8). The center of mass is 31 inches from one end lengthwise, and centered heightwise and widthwise.

I drew an image: http://www.xdemi.com/hovcalc/delirium.bmp [Broken]

Basically, we need the moment of inertia of this object. Two forces are going to be applied at the top-back of the box-frame, and we want to calculate the turning radius. (This is for a hovercraft). We dont' really care about the height-direction. We just need turning radius in the length/width plane. So I suppose we can forget about the height factor.

What is the moment of inertia if the center of mass is offset lengthwise?

Actually, if you know how to calculate the radius or whatever just by knowing the forces and the information I gave you, then that'd be great. Because we could care less about the moment of inertia if we could find the radius of turning.

Last edited by a moderator: May 1, 2017
2. Jan 28, 2005

### FredGarvin

Why is the CG offset on a symetric object? It is hard to tell from your diagram. Is it because it is not homogeneous material? Is the frame made of different members or is it one whole piece?

I am not familiar with any calculations regarding turning radius specifically. However, we can answer the moment of inertia problem.

3. Jan 28, 2005

### pyrexyn

It is not a evenly distributed weight, and not homogneous. However, we found some equations in a text book that helped us. Thank you anyway.