Question:-
With reference to Turbojet and Rocket engines, consider the following statements:
1. Efficiency of Rocket engines is higher than that of Jet engines.
2. Exit velocities of exhaust gases in Rocket engines are much higher than those in Jet engines.
3. Stagnation conditions exist at the combustion chamber in Rocket engines.
4. Rocket engines are air-breathing engines.
Which of these statements are correct?
Option (A)
1 and 2
Option (B)
1,3 and 4
Option(C)
2,3 and 4
Option(D)
1,2 and 3
Correct Option:
(A)
Question Solution:
Rocket properties efficiency

Where Ca ® forward velocity of rocket Cj ® velocity of jet
The jet propulsion efficiency of rocket approaches 100% as (CJ/Ca) approaches unity and it lower on either side. But where as for the propeller and turbojet the flights velocity cannot exceed the jet velocity if the thrust is to be positive, for the rocket the jet velocity is independent of forward motion the Cj can be than, equal to or greater than Ca.
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