Fluid Pressure

Fluid Pressure

Have you ever observed why the nails end with a sharp point, while sipping Cool drink from a straw, have you noticed that you actually suck the air out of the straw? Why and how does this happen? To answer all this question lies in the concept of pressure. While you sip the Cool drink, you are actually applying pressure. What is a pressure?

What is a Pressure?

Pressure is the ratio of the force applied to the surface area over which force is applied. The amount of force exerted on a surface to the area.

What is a Fluid Pressure?

Fluid Pressure is a measurement of the force per unit area on an object in the fluid or on the surface of a closed container. This pressure can be caused by gravity, acceleration or by forces outside a closed container. Since fluid has no definite shape, its pressure applies in all direction. Fluid pressure can also be amplified through hydraulic mechanisms and changes in the velocity of the fluid.

Formula to find the Fluid Pressure: The pressure exerted by a static fluid or hydrostatic pressure, is the pressure in an equilibrium system that depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity. Its units are the same as pressure in general, N/m². The formula for pressure in a fluid is given:

Pfluid = P + ρgh


P = Pressure at the reference point,

Pfluid = Pressure at a point in a fluid,

ρ = Density of the fluid = mass (m)/ Volume (V).

g = Acceleration due to gravity,

h = Height from the reference point.

P₀ = Atmospheric Pressure.

If the fluid is subjected to atmospheric pressure than the total pressure on the system is Pfluid = P₀ + ρgh.