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Homework Help: PE Farmer

  1. Oct 25, 2005 #1
    A farmer uses a pump to lift water from a river to a arable land who lies 5.0m higher than the river. The pump exhaust an electrical effect of 1.0kW but only 65% is used to do the lifting. ok A) I have resolved the lifting work is 0,65*60 = 39kJ

    But B) is harder,,,, how much water is pumped up during a minute ...?

    I have no idea how to solv this please help me
     
  2. jcsd
  3. Oct 25, 2005 #2

    Päällikkö

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    Homework Helper

    In A) you've apparently solved how much work is used to lifting the water a minute.
    During this minute, how much water is lifted?
    Is the anwer in kg or m3? Doesn't really matter, you know their relation.

    What is the energy required to lift a ball of mass m to height h?
     
  4. Oct 25, 2005 #3

    mrjeffy321

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    Science Advisor

    You know that 65% of the pumps power (1 kW) is used to lift water.
    This means that every second, 650 J of energy is used by the pump to list water, multiply by 60 to get energy per minute.
    You know how much energy it will take to lift m kilograms of water h distance up against gravity g (mgh), since in this problem h and g are givens/constants, so just solve for m.
     
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