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Homework Help: Stumped on Moments / Forces diagram qn. Help!

  1. May 16, 2010 #1
    1. 1. The problem statement, all variables and given/known data

    Ok. I'm given a force diagram, and I have to figure out the reaction forces at the two points on the ground.


    answer key: (498.1N↑; 104.2N→, 92.8N↑)

    2. Relevant equations

    Ok. I only got so far as the x-reaction force at the pivot... 600 sin 10 = <- 104.2N

    3. The attempt at a solution

    Total y-reaction forces - 600 cos 10 = 590.88N

    600 cos 10 = 590.88N
    600 sin 10 = 104.2N

    root 0.2^2 x 0.3^2 = 0.36m

    104.19N x 0.3m = 31.257Nm
    590.88N x 0.2m = 118.177 Nm

    498.1N + 92.8N = 590.9N

    i cant figure out how to get 498.1N and 92.8N at the two points respectively...
    anyone can show how to achieve the answer? Thx
  2. jcsd
  3. May 16, 2010 #2


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    Science Advisor
    Homework Helper
    Gold Member

    Sum of moments about any point = 0. Try summing moments of all forces about the hinge to solve for the vertical reaction at the left support. Watch plus and minus signs (ccw and cw moments). Don't forget the moment from both the vertical and horizontal components of the appied force.
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