Statics For Dummies
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In statics, moments are effects (of a force) that cause rotation. When computing equilibrium, you must be able to calculate a moment for every force on your free-body diagram. To determine a force's moment, you use one of two different calculations, as you can see in the following list.

  • Scalar calculation (for two dimensions): To calculate the moment about a Point O in scalar calculations, you need the magnitude of the force and the perpendicular distance from Point O to the line of action of the Force F.

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  • Vector calculation (for two or three dimensions): To compute the moment vector about a Point O in vector calculations, you must determine the Force F in Cartesian vector form and the position vector from Point O to the line of action of the Force F.

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James H. Allen III, PE, PhD, is a registered professional engineer who teaches courses in the areas of statics, mechanics, structural engineering, and steel design.

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