Static pressure may be expressed as gage pressure, which may be negative or positive. Which option best reflects this statement?

• A. The Pressure Of The Fluid Due To Its Motion
• B. The Actual Pressure Of The Fluid, Associated With Its State
• C. The Differential Between Total And Velocity Pressures In A Dynamic System
• D. Gage Pressure

Answer: (D)

Gauge pressure expresses static pressure relative to atmospheric pressure, and it can be either negative or positive. This matches the statement because static pressure isn’t just an absolute value on its own; it’s commonly described as how much pressure is above or below atmospheric, which is exactly what gauge pressure measures. A reading of zero means atmospheric pressure, a positive reading means pressure higher than atmosphere, and a negative reading means pressure lower than atmosphere. The other descriptions refer to related but different concepts: pressure due to motion is dynamic pressure, not static; the actual pressure associated with the fluid’s state without referencing atmosphere is absolute pressure, which is always above zero and includes atmospheric pressure; and the differential between total and velocity pressures is the dynamic pressure, again not static gauge pressure.