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Jet engines: operating condition for higher propulsive efficiency. Determine at which operating regime a jet engine attains higher propulsive efficiency relative to low-speed operation. Select the best option.

Difficulty: Easy

low speeds
high speeds
low altitudes
high altitudes

Correct Answer: high speeds

Explanation:

Concept/Approach
Propulsive efficiency depends on how closely the jet velocity matches the flight speed. For pure jets, efficiency increases with aircraft speed (up to practical limits), since less kinetic energy is wasted in the exhaust stream for a given thrust.

Final Answer
high speeds.

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