Ok im try to understand how to find the moment of inertia of different shapes by using direct integration. In a lot of the solutions I see they always have this one thing that I dont understand. Example:(adsbygoogle = window.adsbygoogle || []).push({});

Determine by direct integration the moment of inertia of the shaded area

with respect to the y axis.

http://img406.imageshack.us/img406/4816/64329189gz9.jpg [Broken]

WHERE DOES THE 1/3 COME FROM??

I know the formula is

Iy = INTEGRALOF(x^2 dA)

doesnt da = xdy

so that makes it

Iy =INTEGRALOF(x^2 * x *dy)

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# Homework Help: Moment of Inertia of Shapes

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