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Equilibrium of Particles

  1. Feb 6, 2015 #1
    1. The problem statement, all variables and given/known data
    Here is the problem that I am stuck on in my mechanics class.

    https://lh4.googleusercontent.com/ygXVjNfI4iP8xVpEjhxXZlWlDqg_VrM2gCVFLyomOVwWCfcLU78mIcPEc7hEzUqBoACIiQ=w1210-h506
    2. Relevant equations
    F=-kx

    3. The attempt at a solution
    See the attached picture of my work
    https://lh3.googleusercontent.com/dpyJ3aIImPY7kOm33QSuD_bZrqTqVL2DnPjhDp2G0t1wWDM9G5RGHORSXESWWNFp4H7xCfrQrLgu0Y9dzntbhG7AKzM=w1210-h506
    I'm so stuck. I don't know what to do from here.
     
  2. jcsd
  3. Feb 6, 2015 #2

    Nathanael

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    Why do you think the change in length of spring AB is 3 meters?

    P.S.
    Just a tip, there's no reason to find the angles spring AB makes; you only care about the sine or cosine of the angles which corresponds to ratios of the sides of the triangle. Finding (and rounding) the angle, like you did, may lead to less accuracy in the final answer.
     
  4. Feb 6, 2015 #3

    Nathanael

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    Now, about your main problem:

    What can you say about the ratio between "Facx" and "Facy"?
     
  5. Feb 6, 2015 #4

    haruspex

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    Because the unstretched length has been taken as 2m instead of 3m.
     
  6. Feb 7, 2015 #5
    tan(45)=FACy/FACx or, they're directly proportional bc tan(45) = 1
    FACy = FACx
    What do I do with this?
     
  7. Feb 7, 2015 #6

    Nathanael

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    You calculated FACx so now you know FACy. You also calculated FABy. So what is the weight of block D?

    But actually you calculated incorrectly, you'll need to recalculate (but I think you had the right idea). The problem says the unstretched length is 3 meters, not 2 meters.
     
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