Fluid Pressure-Hydrostatic Pressure, Conditions for the Consideration of Fluid Pressure (For CBSE, ICSE, IAS, NET, NRA 2022)

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Fluid Pressure - Hydrostatic Pressure

  • The pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity.
  • It is the pressure at a point within a fluid arising due to the weight of the fluid.
  • The pressure in fluids can be calculated using the following relation.


  • P = Pressure at the reference point
  • = the pressure at a point in a fluid
  • ρ = the density of the fluid
  • g = the acceleration due to gravity (considering earth g = 9.8 m/s)
  • h = the height from the reference point

The pressure from the weight of a column of liquid of area A and height h is

The Weight of a Column of Liquid of Area A

The density of the fluid can be calculated by dividing the mass of the fluid in consideration with the volume of fluid taken.


  • m is the mass of the fluid
  • v is the volume of fluid considered
  • If the fluid is subject to atmospheric pressure than the total pressure on the system is given by


is the atmospheric pressure

Conditions for the Consideration of Fluid Pressure

  • Fluid pressure is considered in two conditions
    • In an open condition or open channel flow
    • In a closed condition or closed conduit
  • The fluid pressure given above is the static fluid pressure or hydrostatic pressure.
  • The pressure which is considered here based only on the depth of fluid because the pressure produced due to fluid movement can be considered negligible.
  • The static fluid pressure does not depend on the surface area, the shape of the fluid container or total volume and mass of the liquid.
  • Here, fluids refer to anything that has the ability to flow. Therefore, this refers to both liquids and gases.

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