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: A Force Question

  1. May 12, 2008 #1
    1. The problem statement, all variables and given/known data
    A force F=-4.3i+2.0j+1.5k Newtons exerts a displacement of d=-0.8i+1.8j+-3.6k metres upon a small (ie mass is negligible) object. If the friction force is equal to Ffr=-0.2,, then what is the net work done upon the object?

    2. Relevant equations

    3. The attempt at a solution
    I know the net work is the sum of all the individual work and the work equation is W=F.D. So i tried to work out the work of the initial force stated by multiplying the force and displacement stated which i got 1.64J. I think the only other work is caused by the friction force but when i try to work that out (because the mass is negligable) i get 0. Can someone please help?
  2. jcsd
  3. May 12, 2008 #2
    Mass is negligible only affects calculating the friction force using [itex]\mu N[/itex], but you already have the friction force. What can you do with it?
  4. May 12, 2008 #3
    could i put it as the force in the work equation and put the distance as the displacement thats stated in the question?
  5. May 12, 2008 #4
  6. May 12, 2008 #5
    so i have 1.64 from the first force i worked out and if i put the friction force into the work equation w= -0.2 x D i get -0.82. If I add the two works i have i get 0.82, but the answer is 1.3.... can you give me hints on what ive done wrong??
  7. May 12, 2008 #6
    I get that also. From where did you get this problem?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook