Which statement describes the thrust mechanism of a jet engine?

• A. Drawing air into the compressor
• B. Impinging of the propelling gases on the outside air
• C. Reaction of the propelling gases
• D. Cooling the turbine

Answer: (C)

Thrust is produced by the reaction to expelling exhaust gases rearward. The engine accelerates a mass of air out the nozzle, giving it a rearward velocity. In doing so, momentum is transferred to the surrounding air, and by Newton’s third law an equal and opposite forward force acts on the engine. This reaction force is what we call thrust.

Other parts of the engine—like drawing air into the compressor or cooling the turbine—are essential to making the engine run, but they describe processes that enable thrust rather than the mechanism that creates it. The idea of the exhaust “impinging on the outside air” isn’t the fundamental thrust mechanism; it’s the rearward acceleration and resulting momentum transfer that matter.