# If the balloon had a volume of 2 L at a depth of 40 m, what was the original volume of the balloon if we assume the pressure at the surface of the water is 14.7 psi?

##### 1 Answer

The volume at the surface is 10 L.

#### Explanation:

The pressure at a depth of 40 m is the hydrostatic pressure of the water plus the atmospheric pressure.

The hydrostatic pressure

#color(blue)(bar(ul(|color(white)(a/a)P = ρghcolor(white)(a/a)|)))" "#

where

∴ The total pressure at 40 m is

Now we can use **Boyle's Law** to calculate the volume of the balloon at the surface.

#color(blue)(bar(ul(|color(white)(a/a) P_1V_1 = P_2V_2color(white)(a/a)|)))" "#

#V_2 = V_1 × P_1/P_2#

In your problem,

∴