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Energy, Thermal Expansion

  1. Apr 29, 2009 #1
    1. The problem statement, all variables and given/known data
    An aluminum rod is 23.0 cm long at 20°C and has a mass of 350 g. If 12500 J of energy is added to the rod by heat, what is the change in length of the rod?

    Answer is in mm

    2. Relevant equations
    Q=m*c*delta T
    deltaL=alpha*L0*deltaT
    alpha=24x10^-6
    c=900j/kg


    3. The attempt at a solution
    12500=.35kg*900(Tf-20C)
    Tf=59.68

    deltaL=24x10^-6*.23m*39.68
    The answer I get is 2.19*10-4m which is wrong
    That /1000 to get mm is 2.19*10-7 which is wrong

    I don't understand what I did wrong...
     
  2. jcsd
  3. Apr 29, 2009 #2

    LowlyPion

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    Homework Helper

    Isn't 2.19*10-4m = .219 mm?
     
  4. Apr 29, 2009 #3
    Whoops...divided instead of multiplied. Thanks.
     
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