ABSTRACT
A fluid is sometimes defined as a substance that takes the shape of its container. More precisely, however, a fluid is a continuous substance which when at rest is unable to support shear forces. Thus, a fluid at rest can exert only normal forces on bounding surfaces. The statics of fluids is referred to as hydrostatics when the fluid is a liquid. This chapter considers the forces on surfaces subject to liquid pressure. A surface submerged in a liquid, such as a gate valve in a dam, the wall of a tank, or a plate in the submerged hull of a ship, is subjected to liquid pressures normal to the surface. If these pressures are sufficiently large, then it is necessary to determine the magnitude of the resultant force Fr on the surface due to pressure distribution and to locate the point, known as the center of pressure, at which this resultant force may be assumed to act.
