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Homework Help: I think the Geometry is what is getting me

  1. Jan 7, 2008 #1
    [SOLVED] I think the Geometry is what is getting me


    So I am doing 26 right now and I can't seem to get the cobwebs cleared out of my head. I know that the max Moment will be 80 kN*m and that will occur when I move point a such that the cable makes a 90 degree angle with the boom.

    At that point x will become the hypoteneuse of a right triangle. I also know that theta is still 30 after the move.

    I should be able to find x by using trig, but for some reason I cannot figure out how to incorporate the 1.5m.

    Any ideas?
  2. jcsd
  3. Jan 7, 2008 #2
    This will be painful to explain in words, but draw a straight line 1.5 m off the ground across the picture, so you have like a triangle on top of a funky trapezoid

    You know the 20 and theta, so you can find the bottom of the triangle/top of the trapezoid

    heh...ok draw a line straight down from where the line you drew intersects the towline

    You know the height of that new little triangle is 1.5m, can you deduce an angle that lets you solve for the bottom of that small triangle(which + the bottom of the big triangle = x)?

    More importantly can you decipher what the hell I just said?
  4. Jan 7, 2008 #3
    I don't know but I will try! thanks!
  5. Jan 7, 2008 #4
    Not so much. What are you getting for x?
    Last edited: Jan 7, 2008
  6. Jan 7, 2008 #5
    Well I'm not gonna actually do it

    but here, you see the words "1.5 m" in your picture? See the little line right above the little arrow right above the word? Finish that line! See the triangle on top of the trapezoid? Go with my instructions from there
  7. Jan 7, 2008 #6
    I think I got it. but using a different method.
    Last edited: Jan 7, 2008
  8. Jan 7, 2008 #7
    Then I will wait for someone else who can confirm my answer. I appreciate the help, but if I am not sure that you are doing correctly, I cannot be sure that I am!

  9. Jan 7, 2008 #8
    Err... What grade are you in?
  10. Jan 7, 2008 #9
    What kind of question is this?
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