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IE of a waterfall

  1. Dec 3, 2006 #1
    1. The problem statement, all variables and given/known data
    The water passing over Victoria Falls, located along the Zambezi River on the border of Zimbabwe and Zambia, drops about 105 m. How much internal energy is produced per kg as a result of the fall?


    2. Relevant equations

    PE=mgh
    KE=mc * deltaT

    3. The attempt at a solution

    PE=33.0067 u * 9.81 * 105= 33998.55134 J
    KE= ??

    How do I calculate KE if they don't give me the temp of the water?
    To get the IE, do I just add KE and PE?

    Thanks
     
  2. jcsd
  3. Dec 3, 2006 #2

    Doc Al

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    Staff: Mentor

    I don't see anyone asking you to caculate the rise in temperature (though you could). All you need to figure out is the increase in internal energy. Calculate the amount of mechanical energy converted to internal energy after the water falls. (Hint: What happens to the kinetic energy when the water crashes at the bottom of the falls.)
     
  4. Dec 3, 2006 #3
    Internal energy is the total energy (the sum of kinetic and potential energies) attributed to the particles of matter.

    So wouldn't I have to calculate PE and KE, then add their values to get the total internal energy?
     
  5. Dec 4, 2006 #4

    Doc Al

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    Staff: Mentor

    I think you need to be more precise and distinguish internal energy from macroscopic mechanical energy. Read this: Internal Energy

    When the water falls and crashes into the rocks (or still water) its ordered, macroscopic KE is transformed into disordered microscopic internal energy. How much KE does 1 kg of water have at the bottom of the falls?
     
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