# Relationship between mass moment of inertia and second moment of area?

## Main Question or Discussion Point

I am trying to create a model in SimMechanics of a simple damped frame. I am very new to this software and structural dynamics as well. I have a copy of "Dynamics of Structures" 3ed by Chopra. In the textbook, the author uses the standard geometric and material properties that I am familiar with to obtain stiffnesses (modulus of elasticity, E & second moment of area, I). Simscape, however, asks for mass and inertia tensor. The latter of which has units of mass*length^2. Is there some sort of relationship between the area moment of inertia and mass moment of inertia? The reason it of importance is because I need to create this model and verify it somehow. If I replicate an example in the textbook, then obviously I'll know if I'm doing things correctly. Unfortunately, the textbook only provides area moment of inertia in it's examples.

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Sorry, the two are totally independent of each other.

Sorry, the two are totally independent of each other.
hmm, does anyone know why there's a difference between the book and simscape then?

Sorry, the two are totally independent of each other.
This isn't really true...

They are different, but still dependent/related to each other...
I've never found this in a book,
but one can show the relation between them by using balance of linear momentum...

The relation is the following:

Imass = $$\rho$$area * Iarea

where

Imass : Mass Moment of Inertia
Iarea : Area Moment of Inertia
$$\rho$$area : area density (kg/m²)

enigma
Staff Emeritus