A manometer is used to measure the air pressure in a tank....

A manometer is used to measure the air pressure in a tank. The fluid used has a specific gravity of 1.25 , and the differential height between the two arms of the manometer is 28 in. If the local atmospheric pressure is $12.7 \mathrm{psia}$, determine the absolute pressure in the tank for the cases of the manometer arm with the $(a)$ higher and $(b)$ lower fluid level being attached to the tank.

Key Concepts

Hydrostatic Pressure

Hydrostatic pressure is the pressure exerted by a fluid at rest due to the force of gravity acting on the fluid column above the point of measurement. This concept is vital in understanding how the height difference in a manometer translates to a pressure difference, as the pressure change is directly proportional to the density of the fluid, gravitational acceleration, and the height of the fluid column.

Manometer

A manometer is an instrument that measures the pressure of a fluid by balancing the weight of the fluid column against the pressure to be measured. It typically consists of a U-shaped tube filled with a fluid, and the difference in fluid levels in the two arms corresponds to the pressure difference between the measured system and the reference pressure, such as atmospheric pressure.

Specific Gravity

Specific gravity is a dimensionless quantity that describes the ratio of the density of a fluid to the density of a reference substance (commonly water for liquids). It allows for the easy determination of a fluid's actual density when combined with the known density of the reference, which is essential in calculating the hydrostatic pressure induced by that fluid.

Absolute and Gauge Pressure

Absolute pressure is the total pressure measured relative to a perfect vacuum, whereas gauge pressure is the pressure measured relative to the local atmospheric pressure. The conversion between these two measurements is crucial when interpreting manometer readings, as the reading must be correctly adjusted depending on whether the instrument senses absolute or gauge pressure.

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