Which statement best describes the thrust produced in this engine description?

Which statement best describes the thrust produced in this engine description?

• A. The air exits the engine and provides thrust to propel the aircraft forward.
• B. The air exits the engine but does not contribute to forward motion.
• C. Thrust is created by cooling the air.
• D. Thrust is produced by the wing.

Answer: (B)

Thrust in a jet engine comes from the engine pushing air backward; the aircraft feels a forward reaction force as a result. In this description, the key idea is that the air leaves the nozzle and the forward push on the airplane is due to the reaction to expelling that air, not because the exhaust gas itself continues to push the aircraft forward after it has exited. So saying the air exits the engine but does not contribute to forward motion highlights that the propulsion effect comes from the engine–air interaction producing a reaction force, rather than the exhaust gas somehow pushing the aircraft while already outside the engine. The other statements don’t describe how jet thrust is generated: thrust isn’t created by cooling the air, it isn’t produced by the wing, and while the exhaust is involved, the simplest way to express it is via the reaction to expelling the air.

Thrust in a jet engine comes from the engine pushing air backward; the aircraft feels a forward reaction force as a result. In this description, the key idea is that the air leaves the nozzle and the forward push on the airplane is due to the reaction to expelling that air, not because the exhaust gas itself continues to push the aircraft forward after it has exited. So saying the air exits the engine but does not contribute to forward motion highlights that the propulsion effect comes from the engine–air interaction producing a reaction force, rather than the exhaust gas somehow pushing the aircraft while already outside the engine. The other statements don’t describe how jet thrust is generated: thrust isn’t created by cooling the air, it isn’t produced by the wing, and while the exhaust is involved, the simplest way to express it is via the reaction to expelling the air.