A liquid in a container exerts pressure because of its weight. For example, if you try to put your finger over the end of a tap when it is turned on, you can feel the pressure of the water in the pipe.
If a fluid (liquid or gas) has a density ρ, its pressure P, at a point due to the fluid of height h, is given by
P = ρgh where g = gravitational acceleration
Therefore, for a given liquid, its pressure:
- increases with depth
- increases with density
For a given point in the fluid, its pressure acts equally in all directions. It does not depend on the shape of containers, only on its depth.
Quiz
Example 1
If the density of sea water is 1150 kgm-3, calculate the pressure below 40m of sea water due to the water alone.
Click for the answer
p=hpg
= 40x1150x10
= 460 000 Pa
= 460 kPa
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