1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

10m Steel Wire Length/ +20 Degrees C

  1. Feb 14, 2008 #1
    [SOLVED] 10m Steel Wire Length/ +20 Degrees C

    1. The problem statement, all variables and given/known data
    10.00-m long steel wire supports a pendulum bob at its end. How many millimeters longer is the wire when the temperature increase by 20.0 C


    2. Relevant equations

    (Delta)L = La(Delta)T
    or
    Change in Length = Length * linear expansion * change in temperature

    Linear Expansion for Steel

    a = 11x10^-6/C


    3. The attempt at a solution

    The problem asks for: How many millimeters longer is the steel wire when the temp increases by 20 Celcius.

    Variables:

    L = 10M
    a = 11x10^-6/C
    (delta)T = (x+20)
    x = original temp

    equation: (delta)L = 10m * (11*10^-6/(x+20)) * (x+20)

    Attempt at Solving:

    110m * 10^-5 (the x+20 cancel out?)

    And then I get confused as what to do. Any help is appreciated, tips are always welcome.
     
  2. jcsd
  3. Feb 14, 2008 #2

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    It is the change in temperature so you don't care about the original temperature
    You had it exactly correct with
    Change in Length = Length * linear expansion * change in temperature

    Remember with these small numbers it is easy to make a calculator slip so estimate first.
    10 ppm * 20 deg = 200ppm = 0.2 parts/thousand = 0.2mm/m so roughly 2mm
     
  4. Feb 14, 2008 #3
    Thanks much. Ill go through again and see if I can come up with the same answer. Im sure yours is correct dont get me wrong, I just need to learn it myself too. You help is unbelievably appreciated.
     
  5. Feb 14, 2008 #4

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    My answer isn't correct (the answer is 2.2mm) I was just making the point that you need to have a 'ball park' estiamte of the answer before you start putting numbers into the caclualtor or you wont know if you made a typo.

    You had exactly the correct method.
     
  6. Feb 14, 2008 #5
    I was just getting back to posting with my answer being around 3mm :) I still need to work on my step by step process though obviously. Thanks again! You rock in my book of various stones. <--that was a joke, bad one, but still a joke!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: 10m Steel Wire Length/ +20 Degrees C
  1. Length of wire (Replies: 1)

  2. Sag in steel wire (Replies: 14)

Loading...