Which statement correctly describes dynamic pressure q and its role in lift?

Which statement correctly describes dynamic pressure q and its role in lift?

• A. It increases with air density and velocity squared, and sets the lift scale together with area and CL
• B. It equals total energy of the airflow
• C. It is independent of velocity
• D. It is the same as stagnation pressure

Answer: (A)

Dynamic pressure represents the kinetic energy of the moving air per unit volume, and it scales with density and the square of speed: q = 1/2 ρ V^2. Because of that, increasing air density or increasing velocity squared raises q. Lift comes from how much air the wing moves through (area) and how effectively the wing converts that motion into lift (lift coefficient, CL). The lift equation L = q S CL shows that, for a given wing area and CL, lift grows directly with dynamic pressure. So the statement that dynamic pressure increases with density and velocity squared and sets the lift scale together with area and CL is the correct description. Dynamic pressure is not the total energy of the airflow; it is only the kinetic energy per unit volume (the 1/2 ρ V^2 term). Stagnation pressure, on the other hand, adds this dynamic pressure to the static pressure (p0 = p + q). It also is not independent of velocity, since q itself depends on V.

Dynamic pressure represents the kinetic energy of the moving air per unit volume, and it scales with density and the square of speed: q = 1/2 ρ V^2. Because of that, increasing air density or increasing velocity squared raises q. Lift comes from how much air the wing moves through (area) and how effectively the wing converts that motion into lift (lift coefficient, CL). The lift equation L = q S CL shows that, for a given wing area and CL, lift grows directly with dynamic pressure. So the statement that dynamic pressure increases with density and velocity squared and sets the lift scale together with area and CL is the correct description.

Dynamic pressure is not the total energy of the airflow; it is only the kinetic energy per unit volume (the 1/2 ρ V^2 term). Stagnation pressure, on the other hand, adds this dynamic pressure to the static pressure (p0 = p + q). It also is not independent of velocity, since q itself depends on V.