### Area Moment of Inertia

The *area moment of inertia* is the second moment of an area
around a given axis:

Comparing with the definition of *mass moment of inertia* in
§B.4.4 above, we see that mass is replaced by area in
the area moment of inertia.

In a planar mass distribution with total mass uniformly
distributed over an area (*i.e.*, a constant mass density of
), the mass moment of inertia is given by the area
moment of inertia times mass-density :

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