2.0 Fluid pressure

2.1 Atmospheric pressure
2.2 Pressure variation with depth
2.3 Measurement of pressure
2.4 Pressure difference in accelerating fluids

Thrust: The total normal force exerted by liquid at rest on a given surface in contact with it is known as thrust of liquid on that surface.

Pressure: It is defined as the thrust acting per unit area of the surface in contact with the liquid.

Consider a small surface of area $dA$ inside the fluid. The thrust force exerted by the fluid on each side is $d{F_ \bot }$.

So, $${\text{Pressure = }}\frac{{{\text{Thrust}}}}{{{\text{Area}}}}$$ or $$P = \frac{{d{F_ \bot }}}{A}$$

Pressure is a scalar quantity

Its dimensional formula is $\left[ {{M^1}{L^{ - 1}}{T^{ - 2}}} \right]$

SI unit of pressure is Pascal $(Pa)$. It is named in honor of Fresh Scientist Blaise Pascal

Units of pressure

$1\;Pascal = 1\;Pa = 1\;N/{m^2}$

$1\;barr = {10^5}\;Pa$

$1\;torr = 133\;Pa$

$1\;mm\;{\text{of }}Hg = 1\;torr = 133\;Pa$

$1\;atm = 1.013 \times {10^5}\;Pa\;\left( {at\;S.T.P.} \right)$

$1\;atm = 1.013 \times {10^6}\;dyne/c{m^2}$