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Truss/equilibrium homework help

  1. Apr 16, 2012 #1
    1. The problem statement, all variables and given/known data

    A horizontal truss, symmetric around its center, of mass 15,000 kg and total length 22m, is placed on two posts as shown in the figure
    Find the downward force that it exerts on each post.

    2. Relevant equations



    3. The attempt at a solution

    do i just take the force (weight and multiply it by distances?)

    I have no clue

    can someone give me a hint?
     

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  2. jcsd
  3. Apr 16, 2012 #2
    Re: truss/equilibrium?

    please!>!>!!>
     
  4. Apr 17, 2012 #3
    Re: truss/equilibrium?

    do I calculate torque?
     
  5. Apr 17, 2012 #4

    PhanthomJay

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    Re: truss/equilibrium?

    Yes, sum torques about one of the support posts = 0 to calculate the force reaction of the other post. Do the same thing in summing torques = 0 about the other post to calculate the force reaction of the first post. Check your work using Newton 1 (the equilibrium condition) in the y direction.

    Note: In actuality, a truss should never be supported this way, the supports should be located at a joint. Doesn't change your answer. though.
     
  6. Apr 17, 2012 #5
    Re: truss/equilibrium?

    do these answers make sense??

    so F Right post= 82771.875 N

    and F Left post = 64378.125 N
     
  7. Apr 17, 2012 #6

    PhanthomJay

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    Re: truss/equilibrium?

    Almost spot on! :cool: I say almost, because there should be just 2 significant figures in your answer. Implying Force right post = 83000 N, and F Left post = 64000 N. Or something like that. At least, get rid of the decimal points! :smile:
     
  8. Apr 17, 2012 #7
    Re: truss/equilibrium?

    thanks so much for your help!!!
     
  9. Apr 17, 2012 #8

    PhanthomJay

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    Re: truss/equilibrium?

    you are very welcome!
     
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