Work, Energy and Power · NEET Preparation Physics

A pump is required to lift 600text{ kg} of water per minute from a well 25text{ m} deep and eject it with a speed of 50text{ m/s}. The power of the p…

Practice question from Work, Energy and Power (NEET Preparation Physics), with the correct answer and a step-by-step solution.

hard · MCQ · Q-B86413

A pump is required to lift 600 kg600\text{ kg} of water per minute from a well 25 m25\text{ m} deep and eject it with a speed of 50 m/s50\text{ m/s}. The power of the pump is (take g=10 m/s2g = 10\text{ m/s}^2):

  1. A.15 kW
  2. B.25 kW
  3. C.37.5 kWCorrect answer
  4. D.50 kW

Solution

Mass per second dmdt=600 kg60 s=10 kg/s\frac{dm}{dt} = \frac{600\text{ kg}}{60\text{ s}} = 10\text{ kg/s}. Total energy per second (Power) = Potential energy per second + Kinetic energy per second = dmdtgh+12dmdtv2\frac{dm}{dt}gh + \frac{1}{2} \frac{dm}{dt}v^2. P=(10)(10)(25)+12(10)(50)2=2500+12500=15000 W=15 kWP = (10)(10)(25) + \frac{1}{2}(10)(50)^2 = 2500 + 12500 = 15000\text{ W} = 15\text{ kW}? Wait: 12(10)(2500)=12500\frac{1}{2}(10)(2500) = 12500, total =15000 W=15 kW= 15000\text{ W} = 15\text{ kW}. Let's check options: A is 15 kW. Let's re-verify: 2500+12500=15000 W=15 kW2500 + 12500 = 15000\text{ W} = 15\text{ kW}. Correct answer is A.

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