Question

What is the pressure on a swimmer 20 m below the surface of water:

• A. 1 atm
• B. 2 atm
• C. 3 atm
• D. 4 atm

Answer 1

The correct option is C 3 atm

Let atmospheric pressure $=P_3=1.05\times {10}^5$ Pa

Pressure $20$m below surface of lake

$P=P_0+\int gh$

$=1.05\times {10}^5+1000\times 9.8\times 20$

$=3.01\times {10}^5$ Pa ($\int \to$ water density $=1000kg/m^3$)

$=3$ atm.