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: The work-energy theorem

  1. Mar 31, 2008 #1
    A particle moving in the x direction is being acted on by a net force F(x)= Cx^2, for some constant C. The particle moves from x_initial= L to x_final= 3L. What is deltaK, the change in kinetic energy of the particle during that time?

    Express your answer in terms of C and L.

    I got 16CL^3 but it keeps saying I'm off by a multiplicative factor. Anyone know where I', going wrong?
  2. jcsd
  3. Mar 31, 2008 #2
    The work done on your particle as it moves in the positive [tex]x[/tex]-direction is:

    [tex]W = \int_{x=L}^{3L} F(x) dx[/tex]

    Interestingly, this is independent of how fast the particle is travelling.

    In your case, you have an explicit form for the force: [tex]F = Cx^2[/tex], so:

    [tex]W = \int_{x=L}^{3L} Cx^2 dx[/tex]

    << rest of complete solution edited out by berkeman >>

    Is this better?
    Last edited by a moderator: Mar 31, 2008
  4. Mar 31, 2008 #3
  5. Mar 31, 2008 #4
    hi pterid ... how do u write formulas ??

    best regards
  6. Mar 31, 2008 #5


    User Avatar

    Staff: Mentor

    pterid, Please do not post complete solutions to homework/coursework questions. Even though this thread was originally (incorrectly) posted in the general technical forums, it is easy to recognize it as a homework/coursework question, and should be treated as such, even before a Mentor notices it and moves it to the Homework Help forums.
  7. Mar 31, 2008 #6


    User Avatar

    Staff: Mentor

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook