First Moment of Area Formula |
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\( Q \;=\; A \cdot \bar y \) ( First Moment Area) \( A \;=\; \dfrac{ Q }{ \bar y } \) \( \bar y \;=\; \dfrac{ Q }{ A } \) |
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| Symbol | English | Metric |
| \( Q \) = First Moment of Area | \(lbm \;/\; in^2 - sec\) | \(kg \;/\; mm^2\) |
| \( A \) = Area Cross-section | \(in^2\) | \(mm^2\) |
| \( \bar y \) = Distance from Centroid of the Area to the reference Axis | \(in\) | \(mm\) |
First moment of area, abbreviated as Q, also called first moment of inertia, is the measurement of a shape's area cross-section relative to an axis, located in space. In practical terms and of relavance to this site, the shape is generally a beam or piece of pipe. It is the resistance of an object to bend around a certain axis. It can be used to determine the location of the centroid, which is the point where the sum of all moments of inertia are equal.
