Which equation correctly represents lift in subsonic aerodynamics?

Which equation correctly represents lift in subsonic aerodynamics?

• A. L = ρ V^2 S Cl
• B. L = 1/2 ρ V S Cl
• C. L = 1/2 ρ V^2 S Cl
• D. L = 1/2 ρ V^2 S Cn

Answer: (C)

Lift in subsonic aerodynamics is determined by how effectively the wing converts dynamic pressure into upward force, scaled by the wing area and the lift coefficient. The dynamic pressure, which depends on air density and the square of the flight speed, is q = 1/2 ρ V^2. Multiply this by the wing area S and the lift coefficient Cl (which reflects wing shape and angle of attack), and you get L = q S Cl = (1/2) ρ V^2 S Cl. This shows why lift grows with air density and especially with speed (through the V^2 term), and how Cl modulates that lift based on how the wing is oriented and designed. The other forms aren’t correct for this standard subsonic expression because they either drop the 1/2 factor, use velocity without squaring (mismatching how dynamic pressure scales with speed), or use a different coefficient (Cn) that represents normal force rather than lift.

Lift in subsonic aerodynamics is determined by how effectively the wing converts dynamic pressure into upward force, scaled by the wing area and the lift coefficient. The dynamic pressure, which depends on air density and the square of the flight speed, is q = 1/2 ρ V^2. Multiply this by the wing area S and the lift coefficient Cl (which reflects wing shape and angle of attack), and you get L = q S Cl = (1/2) ρ V^2 S Cl. This shows why lift grows with air density and especially with speed (through the V^2 term), and how Cl modulates that lift based on how the wing is oriented and designed.

The other forms aren’t correct for this standard subsonic expression because they either drop the 1/2 factor, use velocity without squaring (mismatching how dynamic pressure scales with speed), or use a different coefficient (Cn) that represents normal force rather than lift.