Which of the following is NOT one of the four forces affecting flight?

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

Answer: (A)

The main idea here is that the forces acting on an aircraft are lift, weight, thrust, and drag. Velocity, on the other hand, is a measure of how fast the aircraft is moving, not a force. Lift acts upward to balance weight, keeping the aircraft up; weight pulls downward due to gravity; thrust pushes forward to overcome drag; and drag resists the motion through the air. Velocity influences lift and drag (both increase with speed through dynamic pressure), but it is not itself a force. So velocity is the one that does not belong among the four forces.