ABSTRACT
Pressure is dened as the normal force per unit area exerted by a uid (liquid or gas) on any surface. e surface can be either a solid boundary in contact with the uid or, for purposes of analysis, an imaginary plane drawn through the uid. Only the component of the force normal to the surface needs to be considered for the determination of pressure. Tangential forces that give rise to shear and uid motion will not be a relevant subject of discussion here. In the limit that the surface area approaches zero, the ratio of the dierential normal force to the dierential area represents the pressure at a point on the surface. Furthermore, if there is no shear in the uid, the pressure at any point can be shown to be independent of the orientation of the imaginary surface under consideration. Finally, it should be noted that pressure is not dened as a vector quantity and is therefore nondirectional.
