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Homework Help: Work piano

  1. Oct 29, 2008 #1
    1. The problem statement, all variables and given/known data
    The two ropes are used to lower a 267.18 kg piano 5.34 m from a second-story window to the ground. How much work is done by gravity force? (T1=1864 N, θ1=64°, T2=1231 N, θ2=50°.)
    How much work is done by T1 force?
    How much work is done by T2 force?

    2. Relevant equations

    3. The attempt at a solution
    the first part worked out fine i had gotten
    13982.004 J

    but when I tired the second I got it wrong cause i did
    W=FdCos(angle) and then subtracted it from the answer in the first part
    and had gotten
    -9618.56 J

    and for the third part I just used
    the equation
  2. jcsd
  3. Oct 29, 2008 #2


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    Staff Emeritus
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    Homework Helper

    Don't subtract the answer from the work done by gravity, just calculate W=FdCos(angle) for the answer.

    Yes, do it that way for both T1 and T2.
  4. Oct 29, 2008 #3
    I try but it doesn't work out
    am i missing something???
    is it positive or negative ?? i was thinking its negative goes its going down
  5. Oct 29, 2008 #4


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    Staff Emeritus
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    Yes, since the rope tension act against the direction of motion the work would be negative.

    You need to use the angle between the rope and the direction of movement. You don't simply use 64 and 50 degrees, just because those are the numbers you see in the figure or problem statement.
  6. Oct 29, 2008 #5
    thank u
    it makes sense now
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