Fluids at Rest: Hydrostatics

FLUIDS AT REST: HYDROSTATICS

The study of fluids at rest is based on two principles:

1. Pressure intensity at a point, expressed as force per unit area, is the same in all directions.

2. Pressure is the same at all points in a given horizontal line in a continuous fluid.

The pressure, P, varies with depth, z, in a manner expressed by the hydrostatic equation

dP = -ρgdz                        (2:2)

where ρ is the density of the fluid and g is the gravitational constant. Since water and most other liquids can be regarded as incompressible, the density is independent of the pressure, and integration between the limits P₁ and P₂, z₁ and z₂, gives

P₁ - P₂ = ρg(z₁ z₂)                        (2:3)