An unknown immiscible liquid seeps into the bottom of an open oil tank. Some measurements indicate that the depth of the unknown liquid is 1.5 m and the depth of the oil (specific weight = 8.5 kN/m3) floating on top is 5.0 m. A pressure gage connected to the bottom of the tank reads 65 kPa. What is the specific gravity of the unknown liquid?

The specific weight of unknown liquid is found to be 15 KN/m³

Explanation:

The total pressure in tank is measured to be 65 KPa in the tank. But, the total pressure will be equal to the sum of pressures due to both oil and unknown liquid.

Total Pressure = Pressure of oil + Pressure of unknown liquid

65 KPa = (Specific Weight of oil) (depth of oil) + (Specific Weight of unknown liquid) (depth of unknown liquid)

65 KN/m² = (8.5 KN/m³) (5 m) + (Specific Weight of Unknown Liquid) (1.5 m)

(Specific Weight of Unknown Liquid) (1.5 m) = 65 KN/m² - 42.5 KN/m²

(Specific Weight of Unknown Liquid) = (22.5 KN/m²) / 1.5 m

Specific Weight of Unknown Liquid = 15 KN/m³