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: An applied force varies with position

  1. Nov 11, 2012 #1
    An applied force varies with position according to F = k1 xn− k2, where n = 3,
    k1 = 2.4 N/m3, and k2 = 56 N.
    How much work is done by this force on an object that moves from xi = 5.13 m to xf = 28.2 m?
    Answer in units of kJ

    i keep using the integration equation: w = ∫f(x) dx
    where k1x^4/4 - 56x is the new equation which i plug 28.2m and 5.13m and subtract
    i get 377736.527
    but its wrong, help please?
  2. jcsd
  3. Nov 11, 2012 #2


    User Avatar

    Staff: Mentor

    I haven't checked your arithmetic, but you're attacking the problem in the right way. What's the correct answer that you aren't getting?
  4. Nov 12, 2012 #3


    User Avatar
    Homework Helper

    What is the unit of your result? You need to give the result in units of kJ.

  5. Nov 12, 2012 #4
    About 1515 kJ?
  6. Nov 12, 2012 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    No, I also get 377736; but that's J, so the answer should be 377.7kJ.
  7. Nov 13, 2012 #6


    User Avatar
    Homework Helper

    That is the correct result. Maybe it should be rounded to three digits: 378 kJ.

  8. Nov 13, 2012 #7
    Ok. Left the /4 out.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook