Dynamic pressure q is defined as 1/2 times air density times velocity squared.

• A. 0.5 rho V^3
• B. 0.5 rho V^2
• C. rho V
• D. 2 rho V^2

Answer: (B)

Dynamic pressure represents the kinetic energy per unit volume of moving air and is used in Bernoulli’s principle and Pitot-static measurements. It is defined as q = 1/2 ρ V^2, where ρ is air density and V is velocity. The correct expression, 0.5 ρ V^2, matches this definition exactly and gives the correct units (Pa, or N/m^2) since density (kg/m^3) times velocity squared (m^2/s^2) times 1/2 yields kg/(m·s^2) per m^2, i.e., pressure.

The other forms don’t fit: 0.5 ρ V^3 has the wrong dependence on velocity and yields incorrect units; ρ V has units of momentum flux, not pressure; and 2 ρ V^2 would be twice the dynamic pressure, not the correct value.