Which statement about the Pitot tube is true?

Which statement about the Pitot tube is true?

• A. It directly measures stagnation pressure
• B. It requires integration of the velocity field to determine speed
• C. It measures dynamic pressure only
• D. It uses thermal expansion to infer velocity

Answer: (A)

The Pitot tube measures stagnation pressure directly by facing the flow so that the moving fluid is brought to rest at the opening, converting its kinetic energy into a pressure rise. This stagnation (total) pressure is what the tube reads. To get velocity, you also measure the static pressure with a separate port; the difference between stagnation and static pressures is the dynamic pressure, which equals 1/2 ρ v^2 for incompressible flow. Solving for v gives v = sqrt[2(p_t − p_s)/ρ]. So this statement is true because the instrument provides the stagnation pressure directly, and velocity is obtained from the pressure difference, not from integrating a velocity field or from thermal expansion-based methods.

The Pitot tube measures stagnation pressure directly by facing the flow so that the moving fluid is brought to rest at the opening, converting its kinetic energy into a pressure rise. This stagnation (total) pressure is what the tube reads. To get velocity, you also measure the static pressure with a separate port; the difference between stagnation and static pressures is the dynamic pressure, which equals 1/2 ρ v^2 for incompressible flow. Solving for v gives v = sqrt[2(p_t − p_s)/ρ]. So this statement is true because the instrument provides the stagnation pressure directly, and velocity is obtained from the pressure difference, not from integrating a velocity field or from thermal expansion-based methods.