Induced drag is the result of what aerodynamic condition?

• A. An airfoil moving through a fluid
• B. An airfoil developing lift
• C. An airfoil in still air
• D. Interference between surfaces

Answer: (B)

Induced drag arises when the wing is producing lift. As a finite-span airfoil generates lift, it deflects the airflow downward, creating wingtip vortices and a downwash behind the wing. This downwash tilts the effective lift vector backward relative to the flight path, giving a backward, drag-producing component of the force on the wing. So the drag that results is inherently tied to lift generation.

If there’s no lift being produced, there isn’t induced drag in the same sense. The other options aren’t the cause: simply moving through a fluid is general drag but not specifically induced drag; still air provides no flow to create lift and thus no induced drag; and interference between surfaces is a separate effect unrelated to the basic lift-induced drag mechanism.