On Sun, 29 Apr 2001, James R. Frysinger wrote:
>
> One "atmosphere" of pressure is 101.325 kPa. Imagine a column of water
> 10 m tall over a 1 m2 area. The volume of that would be 10 m3, with a
> mass of 10 Mg. The weight of 10 Mg is 98 kN, so that column exerts a
> pressure of 98 kPa at its base. Now account for sea water having about
> 3 % greater density than fresh water and the pressure is ~101 kPa.
Same result by the standard equation for the pressure at the bottom of a
column of incompressible liquid: *pressure = density.g.height*.
For water: density = 10^3 kg/m3 (plus about 3% if salt water).
Assume g = 10 m/s2.
Set height = 10 m.
Then p = 10^3 x 10 x10 = 100 kPa, the "same" as Jim's result.
Note. p = rho.g.h is valid for water, but not for air since air is
compressible and its density changes with altitude.
