Fluids
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 ( i ) When the fluid is at rest - hydrostatics ( ii ) 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 upto height h is ( hρg / 2 ).
Pascal ’ s Law
The increase in pressure at a point in the enclosed liquid in equilibrium is transmitted equally in all directions in liquid and to the Walls of the container .
The working of hydraulic lift , hydraulic press and hydraulic brakes are based on Pascal ’ s law .
Atmospheric Pressure
The pressure exerted by the atmosphere on earth is atmospheric pressure .