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.