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Homework Help: A block of ice falls and a part melts

  1. Aug 26, 2010 #1
    [tex]\cdot[/tex]1. The problem statement, all variables and given/known data
    A block of ice falls into a lake who's temperature is 00c.
    Half of a percent of it's mass melts. What is the minimum height the block falls from.

    2. Relevant equations
    The Latent heat of water:L=79.7[Cal/gr]
    Potential energy: EP=mgh

    3. The attempt at a solution
    the potential energy of the block transforms into heat which melts the ice.
    I'm using L, the latent heat in [Cal/Kg] in order to be in the SI unit system and get the height h in meters:
    mgh=79,700[itex]\cdot[/itex]0.005[itex]\cdot[/itex]m
    [itex]\Rightarrow[/itex]h=40[m]
    The answer should be 171[m], according to the book.
     
  2. jcsd
  3. Aug 26, 2010 #2

    kuruman

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    The SI unit for latent heat is Joules/kg not cal/kg.
     
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