Private Pilot License (PPL) Aerodynamics Practice Exam

What are the four forces that act on an airplane in flight?

1. Thrust, Drag, Lift, Weight

2. Thrust, Gravity, Lift, Drag

3. Thrust, Drag, Lift, Mass

4. Thrust, Drag, Lift, Friction

The correct answer is: Thrust, Drag, Lift, Weight

The four forces that act on an airplane in flight are thrust, drag, lift, and weight. Thrust is the forward force produced by the aircraft's engines, allowing it to overcome drag, which is the resistance the aircraft faces as it moves through the air. Lift is the upward force generated by the wings as air flows over and under them, enabling the aircraft to rise off the ground. Weight, which is the force of gravity acting on the aircraft, pulls it downward. The inclusion of "weight" in the correct answer emphasizes the importance of gravity in opposing lift. This dynamic relationship between these four forces is essential for understanding how an aircraft achieves and maintains flight. The other options either use incorrect terms or replace "weight" with irrelevant components. For example, "mass" does not account for gravitational effects in the same way that weight does, and "friction" is not a primary force acting on an airplane during flight but is a resistive force primarily associated with surface interactions rather than aerodynamic behavior. Thus, recognizing that thrust, drag, lift, and weight are the fundamental forces gives a clear framework for analyzing flight dynamics.