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Homework Help: Simple work problem (ramp)

  1. Oct 14, 2012 #1
    1. The problem statement, all variables and given/known data

    http://www.youtube.com/watch?v=cM3t6Td_rYs&feature=plcp


    2. Relevant equations

    W=FΔrCosθ


    3. The attempt at a solution

    My questions: 1) At around 2:30, when he draws out the free body diagram, I don't understand how he comes up with these Equations. For example, ƩFx = Fa - FgSinθ.

    Why is it "-"? Is it because the x component of gravity is acting against the Fa?

    2) Same as above, but how does he come up with the sum of the forces on the Y component?
     
  2. jcsd
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