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Homework Help: Thermal Expansion of a Rod

  1. Jan 18, 2009 #1
    A rod is measured to be exactly 21.81 cm long using a steel ruler at a temperature of 21.5°C. Both the rod and the ruler are placed in an oven with a temperature of 345.0 °C where the rod now measures 21.93 cm using the same ruler. What is the coefficient of thermal expansion for the material of which the rod is made?

    I have spent over 8 hours trying to figure this out and cant. I need help mainly figureing out delta L of the rod. Any help would be greatful
  2. jcsd
  3. Jan 18, 2009 #2
    Hi - Do you know the coefficient of thermal expansion of the steel ruler?

    If so, you can determine how much the the ruler expanded (from point 0 to point 21.93) at 345.0 oC.

    Given that, you know the new length of the rod.

    Try it, see if it works.

    Regards, BobM
    Last edited: Jan 18, 2009
  4. Jan 18, 2009 #3
    11x10^-6 is the coef I have tried what I think is everything and still no luck on the right answer. I am pretty sure I am setting it up right DeltaL = coef L DeltaT but cant seem to work it out to get the right coef for the rod
  5. Jan 18, 2009 #4


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    Maybe try 13*10-6 for the steel ruler?

  6. Jan 24, 2010 #5
    The coefficient of thermal expansion for steel is (10.5e-6), according to my book.
  7. Jan 24, 2010 #6


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    Does it make sense that if you know the new length of the rod, you could easily calculate the rod's coefficient of expansion? If so, can you calculate what 21.93 cm on the ruler would equal if you cooled the ruler down? That would be the real length of the heated rod.
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