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Heat and phase change: latent heat

  1. Nov 22, 2012 #1
    1. The problem statement, all variables and given/known data

    A 42kg block of ice at 0°C is sliding on a horizontal surface. the initial speed of the ice is 7.3 m/s and the final speed is 3.5m/s. Assume that the part of the block that melts has a very small mass and that all the heat generated by kinetic friction goes into the block of ice. Determine the mass of the ice the melts into water

    2. Relevant equations

    Q=mL

    3. The attempt at a solution

    Q=mL + (1/2v^2 final- 1/2v^2initial)?
     
  2. jcsd
  3. Nov 22, 2012 #2

    haruspex

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    What exactly is Q in that equation?
    The right hand side is dimensionally inconsistent. It mixes energy and velocity2.
     
  4. Nov 24, 2012 #3
    q is heat gained or lost; this is the equation they used in the solution so its gotta be right...
     
  5. Nov 24, 2012 #4
    except they multiply not add
     
  6. Nov 24, 2012 #5

    haruspex

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    Not exact enough for Q, and the equation would still be nonsensical.
    I suggest that the equations ought to say
    KE lost = heat gained by ice = mass melted * latent heat of fusion
    So now you just need an expression for the KE lost.
     
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