A vertical ballast column on a maritime vessel is completely filled with fresh water. A pr… — Armed Services Vocational Aptitude Battery (ASVAB)

A vertical ballast column on a maritime vessel is completely filled with fresh water. A pressure gauge is mounted precisely $60\text{ feet}$ below the open surface of the water. If the specific weight of the fresh water is $62.4\text{ lb/ft}^3$ , what is the hydrostatic gauge pressure at this depth in pounds per square inch (psi)?

Answer: 26 psi

Answer

The hydrostatic pressure is 26 psi.

The correct calculation requires two phases: first, determining the pressure based on depth and specific weight, which yields

3744\text{ psf}

(

60 \times 62.4

). Second, converting area units from square feet to square inches by dividing by 144, resulting in exactly

26\text{ psi}

Step-by-Step Solution

Calculate the hydrostatic pressure in pounds per square foot (psf).

62.4\text{ lb/ft}^3 \times 60\text{ ft} = 3744\text{ lb/ft}^2

(psf)

Hydrostatic pressure is the product of the fluid's specific weight and the depth of the fluid column.

Convert the pressure from psf to pounds per square inch (psi).

3744\text{ psf} \div 144\text{ in}^2/\text{ft}^2 = 26\text{ psi}

There are

144\text{ square inches}

1\text{ square foot}

(

12\text{ inches} \times 12\text{ inches}

). Dividing the psf value by 144 converts the units appropriately.

Key Concept

Hydrostatic Pressure Calculation and Unit Conversion

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