What is the relationship between thrust and drag?

Thrust must overcome drag for acceleration is a fundamental principle in aerodynamics and aircraft performance. When an aircraft is in motion, it experiences aerodynamic drag, which is the resistance force opposite to the direction of motion. For the aircraft to accelerate, the thrust produced by the engines must be greater than the drag acting against it.

In a steady level flight, thrust equals drag, allowing the aircraft to maintain constant speed. However, during acceleration, if thrust is not greater than drag, the aircraft cannot increase its speed. This relationship also emphasizes the importance of engine performance and efficiency when designing and operating aircraft, especially during various phases of flight where different forces come into play.

Other options do not accurately reflect the dynamics of thrust and drag. For example, equal thrust and drag at takeoff does not consider the need for the aircraft to overcome drag to become airborne. The assertion that thrust is independent of drag undermines the basic aerodynamic principles, and stating that drag is only relevant during landing ignores its critical role throughout all flight phases.