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!

Simple integration for Work

  1. Mar 5, 2010 #1
    1. The problem statement, all variables and given/known data
    An applied force varies with position according to F = k1xn - k2, where n = 3, k1 = 8.3 N/m3, and k2 = 87 N. How much work is done by this force on an object that moves from xi = 6.47 m to xf = 14.9 m? Answer in units of kJ.

    2. Relevant equations

    W = k1 x4/4 ]from the integral of x1 to x2
    - k2x]from x1to x2
    3. The attempt at a solution
    I plugged in everything, and I got 96.778 at first, then I thought I should use x33/3, then I got 6.543478 kJ.
    I got both them wrong, did I do the calculation wrong? Please help, thanks. :D

    Last edited: Mar 5, 2010
  2. jcsd
  3. Mar 5, 2010 #2


    User Avatar
    Homework Helper

    Agree with W = k1 x^4/4 - k2x from x1 to x2.
    I got about -15000.
  4. Mar 5, 2010 #3
    I still didn't get that answer. :(
  5. Mar 5, 2010 #4


    User Avatar
    Homework Helper

    It is really W = k1 x^4/4 - k2 x , and I got 97904, similar to your result. Use enough digits during the calculations.

  6. Mar 5, 2010 #5
    I found my mistake, thank you very much.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook