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: Using parameterisation to calculate work done by force

  1. Jul 19, 2017 #1
    A force F = -K(yi + xj) (K is a positive constant) acts on a particle moving in the x-y plane. Starting from the origin, the particle is taken along the positive x-axis to the point (a, 0) and then parallel to the y-axis to the point (a, a). What is the total work done by the force F on the particle.

    My attempt:

    As the final position of the particle is (a, a) so I get the following using parameterisation for 0 <= t <= 1

    x = at
    y = at

    Thus the work done,

    W = integration -k(ydx + xdy)
    = integration -k(atdt + atdt)
    = integration -k(2atdt)
    = -2ak integration (tdt)
    = -ak [t]^2
    = -ak

    What am I doing wrong here?
  2. jcsd
  3. Jul 19, 2017 #2


    User Avatar
    Science Advisor

    What are dx and dy?
  4. Jul 19, 2017 #3

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Why do you go along a straight line from (0,0) to (a,a)? The question said to go along the sides of the square. Of course, for some types of forces the work done is independent of the path, but is that the case here?

    Anyway, even for the diagonal path, have you double-checked your work?
    Last edited: Jul 19, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted