Which force is produced by a propeller or engine that moves the aircraft forward?

Thrust is the forward force produced by a propeller or engine that propels the aircraft through the air. This force results from the engine's design, which creates a difference in pressure as it expels air backward, effectively pushing the aircraft forward due to Newton's third law of motion—every action has an equal and opposite reaction.

In flight dynamics, thrust is essential for overcoming drag, which is the aerodynamic resistance faced by the aircraft as it moves through the air. Additionally, lift is the upward force that counteracts weight, allowing the aircraft to ascend, while weight is the force due to gravity acting on the aircraft's mass. Understanding the role of thrust is crucial in aerodynamics as it directly affects an aircraft's speed and ability to ascend, maneuver, or maintain level flight.