1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Work done by springs in a series

  1. Feb 17, 2008 #1
    1. The problem statement, all variables and given/known data
    Two springs, with force constants k1 and k2, are connected in series, as shown in the figure

    How much work is required to stretch this system a distance x from the equilibrium position?
    2. Relevant equations


    3. The attempt at a solution

    I have no idea how to derive this. I mean I've looked on the wikipedia article on hooke's law and figured that I just change the equation to W=1/2 (1/k1 + 1/k2)x^2

    I'm guessing the problem with this is that the distances that the two stretch are not equal because of the different spring constants but I don't know how to go about showing this in an equation.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 17, 2008 #2
    is that 1/(2kx^2) or (1/2k)x^2
  4. Feb 17, 2008 #3
    it is (1/2k)x^2
  5. Feb 17, 2008 #4
    using 1/kt=1/k1+1/k2. Substitute into elastic potential energy equation.

    Edit: forget that... Misunderstood your question I think.
    Last edited: Feb 17, 2008
  6. Feb 17, 2008 #5
    i did that
    W=1/2 (1/k1 + 1/k2)x^2

    and this was wrong
  7. Feb 17, 2008 #6
    I know. That'd why I edited and said forget it, Lol.
  8. Feb 17, 2008 #7
    ah i see. so any other takers.
  9. Feb 18, 2008 #8
    still need help. is my theory about distances being different right?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook