Which term refers to the force that acts opposite to thrust in the airflow over a wing?

• A. Lift
• B. Weight
• C. Drag
• D. Thrust

Answer: (C)

Drag is the aerodynamic force that opposes the aircraft’s forward motion through the air. It acts opposite to thrust along the direction of flight, slowing the aircraft and requiring the engine to produce enough thrust to overcome it.

Lift and weight are perpendicular to the flight path—lift raises the aircraft, weight pulls it downward. Thrust is the forward force that drives the aircraft ahead. In steady, level flight, thrust balances drag, but drag is the force that resists forward motion. Drag comes from air resistance on surfaces (parasite drag) and from the wing’s lift generation (induced drag), with the balance between drag and thrust changing as speed changes.