Which aerodynamic force opposes movement through the air?

Drag is the aerodynamic force that opposes movement through the air. It acts in the opposite direction to the aircraft's forward motion, creating resistance that must be overcome for the aircraft to advance.

As an aircraft moves through the atmosphere, it displaces air in front of it, causing resistance. This resistance is primarily due to the friction between the air and the surface of the aircraft, as well as changes in air pressure around the aircraft's body. Drag increases with speed and is influenced by factors such as the shape of the aircraft, surface roughness, and the density of the air. To maintain flight, especially at higher speeds, pilots and engineers must consider drag in their calculations and design, as it significantly affects fuel efficiency and performance.

Understanding drag is critical for pilots during various phases of flight, such as takeoff, cruising, and landing, where managing speed and drag is essential for safe and efficient operations.