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First moment of areaThe first moment of area, sometimes misnamed as the first moment of inertia, is based in the mathematical construct moments in metric spaces, stating that the moment of area equals the summation of area times distance to an axis [Σ(a x d)]. It is a measure of the distribution of the area of a shape in relationship to an axis. First moment of area is commonly used in engineering applications to determine the centroid of an object or the statical moment of area. Additional recommended knowledge
DefinitionGiven an area of any shape, and division of that area into very small, equalsized, elemental areas (dA), and given an xy axis, where from each elemental area is measured, that is the distances to each elemental area is known as y_{i} and x_{i}, therefore the first moment of area in the "X" and "Y" directions are respectively: and . The SI unit for first moment of area is metre to the third power (m^{3}). In the American Engineering and Gravitational systems the unit is foot to the third power (ft^{3}) or more commonly inch^{3}. Statical moment of areaThe static or statical moment of area, usually denoted by the symbol Q, is a property of a shape that is used to predict its resistance to shear stress. By definition: , where
Shear Stress in a Semimonocoque StructureThe equation for shear flow in a particular web section of the crosssection of a semimonocoque structure is:
Shear stress may now be calculated using the following equation:
See also


This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "First_moment_of_area". A list of authors is available in Wikipedia. 