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Linear thermal expansion, a space between two metal rods

  1. Apr 4, 2009 #1
    Problem: The brass bar and the aluminum bar are each attached to an immovable wall. At 21.8 °C the air gap between the rods is 1.33 x 10-3 m. At what temperature will the gap be closed? length of brass is 2.0 meters, aluminum is 1.o meters


    Why my solution isnt working I'm not entirely sure, but I feel it may simply be errors in my calculus.



    The attempt at a solution
    aAlum= 23E-6 aBrass=19E-6

    23E-6(1.0)chngT+19E-6(2.0)chngT=1.33E-3m
    chngT(23E-6(1.0)+19E-6(2.0))=1.33E-3m
    chngT=1.33E-3m/((23E-6(1.0)+19E-6(2.0))
    chngT=20.78125
    21.80+20.78125=42.58125C
     
  2. jcsd
  3. Feb 4, 2012 #2
    Final Temperature : T
    Initial Temperature : 21.8°C
    Air gap between the rod/ Changes in Length of brass & aluminium bar: 1.33e-3m

    Delta length of Brass + Delta length in Aluminium = 1.33e-3m
    19e-6 x 2 x ( T-28) + 23e-6 x 1 x (T-28) = 1.33e-3m
    6.1e-5T = 3.008e-3
    T=49.31°C #
     
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