Which unit is used to express the density of water in imperial units?

• A. kg/m^3
• B. n/m^3
• C. lb/ft^3
• D. psi

Answer: (C)

The density of water in imperial units is expressed in pounds per cubic foot (lb/ft³). This unit measures mass (in pounds) over a specified volume (in cubic feet), making it suitable for describing the density of substances in a way that aligns with the imperial measurement system commonly used in the United States.

In practical applications, the density of water is typically about 62.4 lb/ft³ at standard temperature and pressure. This value is widely referenced in engineering calculations involving fluid mechanics, hydrology, and environmental engineering. Knowing the density of water in this format allows engineers to perform necessary calculations related to buoyancy, pressure, and fluid flow, as well as to design systems that appropriately account for the weight of water in various structures.

Other units mentioned do not represent water density in the imperial system. For example, kg/m³ is a metric unit for density, and n/m³ is a unit for pressure, not density. Psi (pounds per square inch) measures pressure, which is unrelated to density. Therefore, lb/ft³ is the correct and applicable unit for expressing the density of water in imperial units.