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 An aircraft with a turbojet engine flies at a velocity of 100 m/s. If the jet exhaust velocity is 300 m/s, the propulsive efficiency of the engine, assuming a negligible fuel-air ratio, is
  • a)
     0.33
  • b)
    0.50
  • c)
    0.67
  • d)
     0.80 
Correct answer is option 'B'. Can you explain this answer?
Most Upvoted Answer
An aircraft with a turbojet engine flies at a velocity of 100 m/s. If ...
To determine the propulsive efficiency of the turbojet engine, we need to consider the thrust generated by the engine and the power consumed by it.

**Thrust Generated:**
The thrust generated by the engine can be calculated using the equation:
Thrust = mass flow rate * (jet exhaust velocity - flight velocity)

Given:
- Jet exhaust velocity (Vjet) = 300 m/s
- Flight velocity (Vflight) = 100 m/s

The relative velocity between the jet exhaust and the aircraft is (Vjet - Vflight) = 300 - 100 = 200 m/s.

**Power Consumed:**
The power consumed by the engine can be calculated using the equation:
Power = thrust * flight velocity

Substituting the values, we get:
Power = (mass flow rate * (jet exhaust velocity - flight velocity)) * flight velocity
= (mass flow rate * (300 - 100)) * 100

**Propulsive Efficiency:**
The propulsive efficiency of the engine can be calculated using the equation:
Propulsive Efficiency = (Thrust * Flight Velocity) / Power

Substituting the values, we get:
Propulsive Efficiency = ((mass flow rate * (jet exhaust velocity - flight velocity)) * flight velocity) / ((mass flow rate * (300 - 100)) * 100)
= (jet exhaust velocity - flight velocity) / (jet exhaust velocity)
= (300 - 100) / 300
= 200 / 300
= 0.67

Therefore, the propulsive efficiency of the engine is 0.67 or 67%. Since none of the provided options match the calculated value, it seems that there might be an error in the given options.
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An aircraft with a turbojet engine flies at a velocity of 100 m/s. If the jet exhaust velocity is 300 m/s, the propulsive efficiency of the engine, assuming a negligible fuel-air ratio, isa)0.33b)0.50c)0.67d)0.80Correct answer is option 'B'. Can you explain this answer? for GATE 2025 is part of GATE preparation. The Question and answers have been prepared according to the GATE exam syllabus. Information about An aircraft with a turbojet engine flies at a velocity of 100 m/s. If the jet exhaust velocity is 300 m/s, the propulsive efficiency of the engine, assuming a negligible fuel-air ratio, isa)0.33b)0.50c)0.67d)0.80Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for GATE 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An aircraft with a turbojet engine flies at a velocity of 100 m/s. If the jet exhaust velocity is 300 m/s, the propulsive efficiency of the engine, assuming a negligible fuel-air ratio, isa)0.33b)0.50c)0.67d)0.80Correct answer is option 'B'. Can you explain this answer?.
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