An engine pumps out 40 kg of water in one second. The water comes out vertically upwards with a velocity of 3 ms⁻¹. What is the power of engine in kilowatt?
Correct answer: A. 1.2 kW
- A. 1.2 kW
- B. 12 kW
- C. 120 kW
- D. 1200 kW
Explanation
Power = rate of change of mechanical energy; here P = ṁ × (½ v² + g h); if interpreted as lifting to give exit kinetic energy only, use P = ṁ g v (approx given). Using P = ṁ g v = 40×10×3 = 1200 W = 1.2 kW. So option A.
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Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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