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Block on incline: work

  1. Feb 10, 2009 #1
    1. The problem statement, all variables and given/known data
    A horizontal force of magnitude F = 197 N is used to push a box of mass m = 5 kg from rest a distance d = 13 m up a frictionless incline with a slope q = 34°.


    2. Relevant equations
    How much work is done on the box by the gravitational force during this same displacement?


    3. The attempt at a solution
    Wg=mgh
    Wg=5*9.81*7.3
    i got 7.3 by using sin34=h/13
    Wg=358.1 J
    The answer i got is wrong according to the online hw. What am i missing? did i use the wrong formula?
     
  2. jcsd
  3. Feb 10, 2009 #2

    LowlyPion

    User Avatar
    Homework Helper

    Maybe it would be negative?

    Work by you is +, work by gravity is stored as potential = (-)?
     
  4. Feb 10, 2009 #3
    wow, it is negative. thank you very much!
     
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