## Tuesday, June 15, 2010

### UNDERSTANDING PRESSURE IN LIQUIDS

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:
i. increases with depth
ii. 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.

Agus Salim said...

very good, but i had no idea... what does it means "deep water"?

selvesini narasingam said...

p=hpg
=40x1150x10
= 46 kPa
more than 46 kPa!!
M i correct???

Fizik said...

p= hpg
= 40x1150x10
= 460 000 Pa
= 460 kPa