Pressure at free surface of a water lake is P1, while at a point at depth h below it’s free surface is P2. (a) How are P1 and P2 related ? (b) Which is more P1 or P2 ?

(a) As we know,

Total pressure in a liquid at a depth h is P₂

= atmospheric pressure acting on the surface (P₁) + pressure due to liquid column (h ρ g)

= P₁ + h ρ g

Hence,

P₂ = P₁ + h ρ g

(b) From the above expression we observe that,

P₂ > P₁