What is the equation for lift?

What is the equation for lift?

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

Answer: (C)

Lift comes from the wing’s ability to convert the air’s motion into an upward force, and it scales with three things: how effective the wing is at producing lift (the lift coefficient), the air’s density and the speed of the airflow (dynamic pressure), and the wing area. The standard expression is L = Cl × q × S, where q is dynamic pressure equal to 1/2 ρ V^2. Substituting q gives L = Cl × 1/2 × ρ × V^2 × S. This shows lift grows with speed (through V^2), density, and wing area, and is scaled by how shape and angle of the wing generate lift (Cl). The other forms don’t capture the way lift depends on dynamic pressure or include weight or the wrong velocity dependence, so they don’t produce the correct force.

Lift comes from the wing’s ability to convert the air’s motion into an upward force, and it scales with three things: how effective the wing is at producing lift (the lift coefficient), the air’s density and the speed of the airflow (dynamic pressure), and the wing area. The standard expression is L = Cl × q × S, where q is dynamic pressure equal to 1/2 ρ V^2. Substituting q gives L = Cl × 1/2 × ρ × V^2 × S. This shows lift grows with speed (through V^2), density, and wing area, and is scaled by how shape and angle of the wing generate lift (Cl). The other forms don’t capture the way lift depends on dynamic pressure or include weight or the wrong velocity dependence, so they don’t produce the correct force.