= Moment of inertia of a uniform square plate
{title2=$I=Ms^2/6$}
A uniform square of side $s$ has the displayed <moment of inertia> about the perpendicular axis through its centre. Integrating $x^2+y^2$ over $[-s/2,s/2]^2$ gives $s^4/6$; multiplying by the <surface mass density> $M/s^2$ gives the result. A square prism of any uniform thickness has the same axial formula when expressed in terms of its total mass. If the side is denoted $2a$ instead, the result is $2Ma^2/3$, so the side-length convention must be specified before substituting numerical data into a <normal mode> calculation.
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