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Melting a snowball by throwing it at a wall

  1. Feb 7, 2013 #1
    1. The problem statement, all variables and given/known data

    You throw a snowball at 0.0 Celsius at a brick wall. If you want it to melt completely, how fast will you have to throw it?

    2. Relevant equations

    [itex] Q = mL [/itex]

    [itex] E_k = \frac{1}{2} mv^2 [/itex]

    3. The attempt at a solution

    I initially reasoned that you would use Q = mL to find the energy needed to melt it and then substitute that into the Kinetic energy formula, giving:

    [itex] mL = \frac{1}{2} mv^2 [/itex]

    However, I am given no information regarding the mass of the snowball and haven't figured out a method to find that mass.
    Any suggestions?

    Thanks,
     
  2. jcsd
  3. Feb 7, 2013 #2
    Why do you need mass when it cancels out in the equation you formed? :confused:
     
  4. Feb 7, 2013 #3

    trollcast

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    Just assume that mass equals 1.
     
  5. Feb 7, 2013 #4
    Ah!
    I didn't notice that. Thanks.

    I'm now at

    [itex]L = \frac{1}{2}v^2 [/itex]

    Edit:

    I changed 334 j/g to 334000 j/kg and arrived at around 800 m/s
     
    Last edited: Feb 7, 2013
  6. Feb 7, 2013 #5

    haruspex

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    2016 Award

    If you want your working checked, please post it.
     
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