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Unformatted text preview: Hydrostatic Forces on Plane Surfaces (Section 3-5, engel and Cimbala)
Liquid surface, open to air pressure P0 (P0 is usually Patm) The centroid C is the mathematical center of the plate's area. We calculate the average pressure at the centroid. However, the resultant pressure force acts not at C, but at CP, the center of pressure. Because pressure increases as you go down in the liquid, the "pressure prism" is thicker towards the bottom, and therefore, the center of pressure CP is located below the centroid C. Average pressure Pave is easy to find it is simply the pressure at the centroid C of the plate's surface area. (See the text, Fig. 3-28, for centroids of many common shapes.) The resultant force FR on the face of the plate is equal to the pressure PC at the centroid C times the area of the plate. I.e., FR = PC A
But, FR does not act at the centroid! The line of action of the resultant hydrostatic force passes through the center of pressure CP and acts perpendicular to the plate ...
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This note was uploaded on 07/23/2008 for the course ME 33 taught by Professor Cimbala during the Fall '05 term at Pennsylvania State University, University Park.
- Fall '05