Which concept is the pressure present when a fluid is at rest?

• A. Dynamic pressure
• B. Velocity
• C. Static pressure
• D. Elevation

Answer: (C)

When a fluid is at rest, there is no motion to generate kinetic energy, so dynamic pressure is not present. The pressure that exists everywhere in the fluid in all directions is static pressure, which arises from the weight of the fluid above and is transmitted through the fluid (Pascal’s principle). In hydrostatics this pressure can be described by P = P0 + ρgh, showing how it increases with depth (or with lower elevation). Elevation alone isn’t pressure, and velocity describes movement, not the pressure when the fluid is stationary. So the pressure present when a fluid is at rest is static pressure.