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Conservation of energy water turbine problem

  1. Feb 10, 2013 #1
    1. The problem statement, all variables and given/known data

    a3jsbs.jpg

    2. Relevant equations

    mgh=1/2mv^2

    3. The attempt at a solution

    7.1) 200*1000=200000kg

    7.2) Must I use mgh? They asked for kinetic energy but energy is conserved so:
    200000*9.8*150
    = 2.9*10^8 J

    7.3) Ep=Ek
    2.9*10^8=1/2*200000*v^2
    v=53.8 m.s

    7.4) 85% of 2.9*10^8
    = 2.5*10^8 J

    7.5) It gets converted into heat and sound when it hits the turbine.

    All good?
     
  2. jcsd
  3. Feb 10, 2013 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    The electrical power output is energy per time, it has Watts as unit.
    The numbers look fine, but you should keep their units in the calculations. In addition, it would be easier to understand your solutions if you start with the formulas first, and plug in numbers afterwards.
     
  4. Feb 10, 2013 #3
    p=w/t, how to find time?, must I use equations of motion?
     
  5. Feb 10, 2013 #4
    Nope. You already know that the time is 1sec.
     
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