Hey there Physics Forums!!(adsbygoogle = window.adsbygoogle || []).push({});

I kept getting links to you guys cropping up in Google searches, so when I got stuck with something I figured I'd register and ask here -- seems like a pretty knowledgeable. :)

Anyhow, I'm trying to calculate the mass moment of inertia for a flat, triangle-shaped plate. The axis of rotation goes through the center of mass of the plate, and is parallel to the Z axis if the vertices of the triangle are defined on the X and Y axes. According to:

http://www.efunda.com/math/areas/triangle.cfm

the formula for this is

http://www.efunda.com/math/areas/images/triangle12.gif .

Now, this is assuming that the area density is equal to 1. If I want to find the actual mass moment of inertia of the triangle, and I know the area density, would I just multiply the final result by the area density? I'm skeptical that it's that simple. Would I need to isolate the formula for the are of a triangle out of that equation, multiply it by the area density coefficient, and then plug that back into the equation by working backwards (if that even makes sense :| )?

Any help is really appreciated!

Peace and love,

dgm

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Moment of inertia & area density

**Physics Forums | Science Articles, Homework Help, Discussion**