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Calculating work

  1. Oct 27, 2009 #1
    1. The problem statement, all variables and given/known data
    There is a piano that is being lowered 5 m. It has gravity force acting in y-direction (down) of 2500 N. Then it has two ropes attached, they are vectors that are pointing up and out. so T1 is 1830N [W60[tex]\circ[/tex]N] and T2 is 1295N [E45[tex]\circ[/tex]N]


    2. Relevant equations
    so the work by gravity is 12500 J
    the work by T1 is 4575 J (opposite direction to work by gravity)

    3. The attempt at a solution
    so it would make sense that the work by T2 is somewhere close to 7000 J so that the net work is 0. but when i calculate it i get around 4000 J. Can someone check my math...

    For T2:
    W = Fcos[tex]\theta[/tex][tex]\Delta[/tex]r
    = 1295*cos45*(5)
    = 4579 J

    ???? - thnx!
     
  2. jcsd
  3. Oct 28, 2009 #2
    Hi there,

    I believe you have a problem with the angle of T1. Becausem, when I verified your calculations, I come to precisely 0 net work.

    Cheers
     
  4. Oct 28, 2009 #3
    oh yes thank you! i was using an angle that gave the component perpendicular to motion :)
     
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