Pressure in fluids

Pressure in fluids

1. Thrust A forever acting normally on a surface is called thrust. Measured in dynes in CGS system and newtons in SI system.

2. Pressure The force acting normally on a surface area is called pressure.

   • Pressure = Thrust upon Area
   • Pressure is a scalar quantity.
   • Unit of pressure When a force of 1N acts normally on an area of 1 sq.m , then the pressure acting on that surface is called 1 pascal.

3. Fluids Any substance which has no fixed shape and can follow is called fluids

   • The momentum imparted per second by the molecules to a given surface gives rise to average force acting on the surface. This average force acting per unit area gives rise to fluid pressure

4. Factors on which the pressure at a point in fluid depends.

   • Pressure in fluids is directly proportional to its height (or depth)
   • Pressure in a fluid is directly proportional to its density
   • Pressure in a fluid is directly proportional to the acceleration due to gravity.
   • Pressure in a fluid is independent if the area of cross section.

5. Laws of fluid pressure

   • Pressure at a point inside the liquid increases with the depth from the free surface of the liquid.
   • Pressure at a point inside the liquid at a given depth increases with the increase in the density of the liquid.
   • Pressure is same in all directions, about a given point within the liquid
   • Pressure is same at all points in horizontal plane at a given depth in a stationary liquid
   • A liquid seeks its own level

6. The force exerted by the air on a unit surface area is called atmospheric pressure.

   • Measured using barometer
     • Fortin's Barometer
     • Mercury Barometer
     • Aneroid Barometer

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