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Homework Help: Work Problem Help!

  1. Oct 12, 2012 #1
    1. The problem statement, all variables and given/known data

    A 31.3 kg sled starts at rest on a horizontal road. The coefficient of kinetic friction between the sled and the road is μk = 0.23. A man pulls the sled a distance 8.75 m along the ground by exerting a constant force of magnitude 257 N on a rope that makes a 23.7o angle above the horizontal. Find:

    2. Relevant equations

    Hm..

    W_f = mgdµ_k?

    3. The attempt at a solution

    Got 618 as the answer, but it's wrong.
     
  2. jcsd
  3. Oct 12, 2012 #2
    first find the net force acting on the sled in the x direction
     
  4. Oct 12, 2012 #3
    OK. What I have is...

    F_net = F_app - F_frictional
    = 257cos(23.7) - 31.3 * 9.81 * 0.23
    ≈ 165

    Then, what? Multiply that by the distance to get the work done?
     
  5. Oct 12, 2012 #4
    Actually, I found the normal force which is 204. Then, I need to use that to determine the work done! My bad.. -___-
     
  6. Oct 12, 2012 #5
    so... problem solved?
     
  7. Oct 12, 2012 #6
    Find what??
     
  8. Oct 12, 2012 #7
    I guess so. Here is what I have...

    W = (2060 - 204 * .23)8.75 = 1650

    Am I on the right track?
     
    Last edited: Oct 12, 2012
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