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: Find potential energy function and show that it is proportional to displacement

  1. Oct 20, 2012 #1
    1. The problem statement, all variables and given/known data
    Find the potential energy function for a spring if the origin is placed at the wall and the unstretched length of the spring is L. Show that with a suitable choice of the constant, this potential function is proportional to the square of the amount that the spring is stretched or compressed.

    2. Relevant equations
    F = d(h(x))/dx (F = force function)
    U(x) = -h(x) (U(x) is potential energy function)

    3. The attempt at a solution

    Force of the spring
    F = -kx

    I integrated F and made the result negative to get the potential energy function
    kx2/2 + C

    But the Textbook solution is:
    kx2/2 - kLx + C

    How do I get -kLx? Also, I'm not sure about how I should start the second part of the problem.
  2. jcsd
  3. Oct 20, 2012 #2
    x is the distance from the wall, so the force is -k(x-L).
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook