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Homework Help: A challenge for professionals

  1. Nov 25, 2008 #1
    1. The problem statement, all variables and given/known data

    metal rod 30cm long expands by 0.075cm when its temp. is raised from 0C to 100C. A rod of diff. metal of the same length expands by 0.045cm for the same rise in temp. A third rod, also 30cm long is made up of pices of each of the above metals placed end-to-end expands 0.065cm between 0C to 100C.

    What is the length of EACH composite bar.

    3. The attempt at a solution

    deltaL=initial L x coefficient of thermal expansion.

    That formula was the similar from some of my friends. I tried it but still i found it out complicated. Thanks in advance to those who helped. God bless
  2. jcsd
  3. Nov 25, 2008 #2


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    The coefficient of thermal expansion is what fraction of it's original length a material expands for each 1deg change in temperature.
    You can find this value for materials A and B from the numbers you are given.

    Your equation isn't quiet correct, it should be: deltaL=initial L x coefficient of thermal expansion x CHANGE IN TEMPERATURE
  4. Nov 25, 2008 #3
    please state your help in equation with explanations. I was able to find the answer but not sure. in my computation the answer 20. I just need a justification in this answer.

  5. Nov 25, 2008 #4


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    This site is to teach people how to answer science questions and help them when they go wrong - we don't just supply answers.
    I suggest you post your calculations of the coeff for the two materials.
    Then we will explain how to do part 2.
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