OHST Practice Exam

What does the measure "one mm of mercury" represent?

1. A unit of temperature

2. A unit of pressure

3. A unit of distance

4. A unit of volume

The correct answer is: A unit of pressure

The measure "one mm of mercury" represents a unit of pressure. It is derived from the height of a column of mercury that is supported by atmospheric pressure. This unit is commonly used in barometers and manometers to measure atmospheric pressure or fluid pressure. The concept originates from Pascal's principle, where a column of liquid exerts pressure based on its height. Typically, one mm of mercury corresponds to a pressure of approximately 133.322 pascals, illustrating its role within the broader context of pressure measurement. The other options do not apply here: temperature is measured in degrees (Celsius, Fahrenheit, or Kelvin), distance is measured in units such as meters or kilometers, and volume is typically expressed in liters or cubic meters. Therefore, recognizing "one mm of mercury" as a unit of pressure is crucial for understanding how pressures are quantified in various scientific and engineering applications.