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Statics Question Moment for a Truss

  • #1

Homework Statement



I need to find the moment about G. Please ignore the question in the image.

http://img13.imageshack.us/img13/6086/4cv0.jpg [Broken]

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Homework Equations



r X F

The Attempt at a Solution



Moment about G = -(30*800) + (-300*50) + 60 A + 17.32*500 + (-17.32*500(4/5)) =0

I keep getting A= 621 N but my solution is saying 721N. I am doing something wrong, not sure what.
 
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Answers and Replies

  • #2
SteamKing
Staff Emeritus
Science Advisor
Homework Helper
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You need to look at the moment produced by both components for the 500 lb load at point I.

The reaction at A should be in lbs rather than newtons.
 
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  • #3
Moment about G = -(30*800) + (-300*50) + 60 A + 17.32*500 + (-17.32*500(4/5)) + (-40*500(3/5)) =0

When I do that I get 821lb? I am still off....
 
  • #4
wrong way its 20 thank you!!
 

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