PRESSURE IN FLUIDS

PRESSURE IN FLUIDS

1. A Force acting normally on a surface is called thrust.

   • It is a vector quantity.
     • ▪C.G.S Unit= dynes ▪S.I Unit=Newton(N)
       • Gravitational unit=kilogram force(kgf) ▪1kgf=9.8N ( approx 10N)

2. The Force acting normally on unit surface area is called pressure.

   • It is a scalar quantity.
   • It is measured in newton per square metre(Nm^-2) or pascal (Pa).
     • one bar=10^5Pa

3. Any substance which has no fixed shape and can flow are called fluids.

   • All liquids and gases are fluids.
   • Fluids exert pressure in all directions
     • The pressure which a fluid exerts on the sides of the containing vessel below its free surface is called lateral pressure.
       • PRESSURE IN a fluid is directly proportional to HEIGHT,density and acceleration due to gravity.
         • PASCAL'S LAW: Whenever any pressure is applied to any part of the boundary of a confined fluid,it is transmitted equally in all directions irrespective of the area on which it acts,and always acts at right angles to the surface of the containing vessel.

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

   • The instrument used for measuring it is barometer,constructed by Torricelli in 1943.
     • Factors which affect the barometric height: •Presence of moisture in mercury. •Presence of dissolved metals in mercury. •Vertical height from sea level. •Temperature of atmosphere. •Presence of moisture in air.
       • The atmospheric pressure at sea level is 1.013×10^5Pa
         • The barometer that does not use any liquid is called Aneroid barometer.

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