Fluids are those substances which can flow when an external force is applied on it. Liquids and gases are fluids. Fluids do not have finite shape but takes the shape of the containing vessel, The total normal force exerted by liquid at rest on a given surface is called thrust of liquid.

The SI unit of thrust is newton.

In fluid mechanics the following properties of fluid would be considered

(1) When the fluid is at rest - hydrostatics

(2) When the fluid is in motion - hydrodynamics

PRESSURE EXERTED BY THE LIQUID

The normal force exerted by a liquid per unit area of the surface in contact is called pressure of liquid or hydrostatic pressure.

Pressure exerted by a liquid column                                                    

p = hρg

Where, h = height of liquid column, ρ = density of liquid and g = acceleration due to gravity

Mean pressure on the walls of a vessel containing liquid up to height h is (hρg / 2).