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Homework Help: Thermo Mixing Question

  1. May 8, 2005 #1
    hi guys, i have a thermodynamics question.

    a 2.50 kg iron object is initially at 650 degrees celsius and dropped into a bucket containing 20kg of water at 25 degrees celsius, what is the final temperature?

    As always it just a matter of applying the formula, but i dont seem to be applying the right one?
    Thanx
     
  2. jcsd
  3. May 8, 2005 #2

    Doc Al

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    Staff: Mentor

    Consider that the net exchange of thermal energy must be zero. Whatever heat flows out of the iron ([itex]Q = m c \Delta T[/itex]) must be equal to the heat flowing into the water. And, once they reach equilibrium, both iron and water end up at the same final temperature.
     
  4. May 8, 2005 #3
    is delta t, t final - t initial or vice versa?
     
  5. May 8, 2005 #4

    Doc Al

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    Staff: Mentor

    I suggest using [itex]\Delta T = T_f - T_i[/itex]. In which case, [itex]Q_{water} = - Q_{iron}[/itex]. (The iron cools down, so its [itex]\Delta T[/itex] is negative.)
     
  6. May 9, 2005 #5
    ok, the specific heat capacity of iron is 440J per degree celsius, right?
    if so i have all the values i need, i just need to transpose the formula to find the final temperature
     
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