If the angle of attack is kept constant and airspeed doubles, the lift produced at the higher speed will be what?

If the angle of attack is kept constant and airspeed doubles, the lift produced at the higher speed will be what?

• A. Doubles
• B. Quadruples
• C. Remains the same
• D. Increases by 1.5 times

Answer: (B)

Lift at a fixed angle of attack scales with dynamic pressure, which is proportional to V^2: L = q S Cl, with q = ½ ρ V^2. If the air density and wing geometry stay the same and the angle of attack doesn’t change, Cl stays about the same, so lift follows V^2. Doubling speed makes V^2 increase by a factor of four, so lift becomes four times larger. That’s why quadruples is the correct result. The other options would require a different dependence on speed or a change in Cl, which isn’t the case here.

Lift at a fixed angle of attack scales with dynamic pressure, which is proportional to V^2: L = q S Cl, with q = ½ ρ V^2. If the air density and wing geometry stay the same and the angle of attack doesn’t change, Cl stays about the same, so lift follows V^2. Doubling speed makes V^2 increase by a factor of four, so lift becomes four times larger. That’s why quadruples is the correct result. The other options would require a different dependence on speed or a change in Cl, which isn’t the case here.