At what depth in a salt water lake is the absolute pressure equal to three times atmospheric pressure ? Density of a sea water = `1.3 xx 10^3 (kg)/m^3`. Atmospheric pressure =`1.013 xx 10^5 N/m^2`.g = `9.8 m/s^2`.

Explanation

Absolute pressure = gauge pressure + atmospheric pressure, From the condition of the problem therefore we have gauge pressure =` 2 xx` atmospheric pressure it h be the required depth
hpg = `2 xx` atmospheric pressure h =` (2 xx 1.013 xx 10^5)/(1.03 xx 10^3 xx 9.8`) = 20 m.