Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Need some direction please. Thermodynamics.

  1. Mar 6, 2008 #1
    1. The problem statement, all variables and given/known data

    Aluminum wing is 30m long at 20*c

    At what temperature would the wing be .05m shorter?

    The coefficient for linear expansion of aluminum is (16 x 10^-6/c)


    I have no idea how to do this. I don't want an answer. Just an equation or a hint on what to do. Thank you very much.
     
  2. jcsd
  3. Mar 7, 2008 #2

    rl.bhat

    User Avatar
    Homework Helper

    What is the relation between the initial length , final length , coefficient of linear expansion and temperature difference?
     
  4. Mar 8, 2008 #3
    I have no idea.
     
  5. Mar 8, 2008 #4

    HallsofIvy

    User Avatar
    Science Advisor

    Where did you get that coefficient? "16 x 10^-6/c" Are you sure of the "units"? What does "/c" mean? You might want to check that.
     
  6. Mar 8, 2008 #5
    Sorry,
    I messed up the coefficient. It's 25 x 10^-6/*C
     
  7. Mar 8, 2008 #6
    I'm sorry if I sound stupid not being able to figure this question out. The truth is I probably have no business being in a physics class. I'm going to school to be a therapist and am taking this class to fill a science requirement. I'm sure there are easier classes I could've taken, but a few months before the semester started I saw that documentary The Elegant Universe and thought hmm... physics looks fun. That blasted Brian Greene and his easy to understand explanations!!!
     
  8. Mar 13, 2008 #7
    Does this look right?

    Aluminum wing is 30m at 20*C. At what temp would it be .05m shorter.
    ∆T = ∆l / α x l
    ∆T = -.05m/(25 x 10-6/*C) x 30m
    ∆T = -66.667
    The wing would be at -46.667*C to be .05m shorter.
     
  9. Mar 13, 2008 #8

    rl.bhat

    User Avatar
    Homework Helper

  10. Mar 13, 2008 #9
    Thank you very much.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook