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Homework Help: Thermal elongation

  1. Sep 14, 2014 #1
    1. The problem statement, all variables and given/known data
    The pendulum of a clock is made of alumina. what is the relative elongation when cooled from 750 fahrenheit to 450?

    2. Relevant equations
    $$L=L_0(1-\alpha \Delta t)$$
    From Fahrenheit to Celsius:
    Coefficient of thermal elongation of alumina: 24E-6^0 celsius

    3. The attempt at a solution
    300 fahrenheit are: ##\Delta t_c=\Delta t_f \frac{5}{9} \Rightarrow \Delta t_c=16.67^0##
    $$\frac{L}{L_0}=\frac{L_0(1-\alpha \Delta t)}{L_0}$$
    $$24E-6^0 \cdot 16.67=0.0004$$
    Exactly, and it It should be 0.00036
  2. jcsd
  3. Sep 14, 2014 #2


    User Avatar

    Staff: Mentor

    Is there a negative sign for its "elongation" when cooled?
  4. Sep 14, 2014 #3
    In the book there isn't a negative sign, but i think it's clear that it shortens in the amount 1-0.00036
  5. Sep 14, 2014 #4
  6. Sep 14, 2014 #5
    It is given in the book and it's aluminium
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