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Resultant and moment

  1. Sep 20, 2013 #1
    1. The problem statement, all variables and given/known data

    I have to determine the resultant R and the moment about O.

    2. Relevant equations

    see the image.

    3. The attempt at a solution

    See the image.

    Attached Files:

  2. jcsd
  3. Sep 21, 2013 #2


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    Hi LMW - Dk! Welcome to PF! :wink:

    Show us what you've tried and where you're stuck, and then we'll know how to help! :smile:
  4. Sep 21, 2013 #3
    See the pictures. I have found the moment and the resultant. However I think it's the wrong method ^^
  5. Sep 21, 2013 #4


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    sorry, i didn't notice your third picture :redface:

    your Fz36 should be minus 36, shouldn't it? :smile:

    (btw, i think most people find it easier to use cos and sin, of angles < 90°, and then use common-sense to decide whether its + or -)

    i don't understand what you did to find the moment :confused:
    can you please type it out in the post?​
  6. Sep 21, 2013 #5
    Well can't you tell me how you would do this problem? how would you find the resultant and the moment?
  7. Sep 21, 2013 #6
    If you click on the second picture then you can see that i have drawn a direction vector. Then i have found the cfross product of the direction vector and the resultant force.
  8. Sep 21, 2013 #7


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    ah, now i understand …

    no, you've crossed the resultant with the position vector for only one of the vectors: you need to cross each vector with its own position vector, and then add (ie, there's no short-cut)

    (and did the minus 36 help?)​
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