Pressure in Liquid - Example 2

Example 2:

Figure above shows the cross section of a sea near a seaside. Find the difference of the pressure between point A and point B. [Density of seawater = 1050kg/m³]

Answer:
Density, ρ = 1050kg/m³
Gravitational Field Strength, g = 10 N/kg

At point A:
Depth, h = 0.8 m
$$\begin{array}{l}{P}_a=h_a\rho g+P_{atm}\\ P_a=(0.8)(1050)(10)+P_{atm}\\ P_a=8400+P_{atm}\end{array}$$
At point B:
Depth, h = 3 m
$$\begin{array}{l}{P}_b=h_b\rho g+P_{atm}\\ P_b=(3)(1050)(10)+P_{atm}\\ P_b=31500+P_{atm}\end{array}$$
Pressure Difference
$$\begin{array}{l}{P}_b-P_a\\ =(31500+P_{atm})-(8400+P_{atm})\\ =23100Pa\end{array}$$