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Homework Help: Truss problem (simple question)

  1. Mar 27, 2013 #1
    1. The problem statement, all variables and given/known data

    Ok, I have everything done for this problem... I just don't understand how they got some of the distances! Just look at the uploaded images...

    - Where did 2/3 m come from? (The vertical distance from the support to E)
    - Where did 1 m come from? (The vertical distance from E to D)

    I calculated different distances, like D - E = 1.67 m using rules of 3 or proportionality.

    I'm sure it's something simple but I just can't see it...

    Thanks in advance

    Attached Files:

    Last edited: Mar 27, 2013
  2. jcsd
  3. Mar 28, 2013 #2


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    You've got to review simple proportions.

    Lookit: the vertical distance from the support to E
    The total vertical distance from A to G is 1 m
    The vertical distance from A to E is x m.
    The horizontal distance from A to G is 6 m
    The horizontal distance from A to E is 4 m

    Writing our proportion, x/4 = 1/6
    solving, x = 4/6 = 2/3 m

    All other distances can be solved in a similar fashion.
  4. Mar 29, 2013 #3
    Great, I see it now... I have been practicing them actually.

    Do you know about any possible source where I can read more about these little "skills" needed for Physics problem solving? (trigonometry stuff, proportions, etc...).

    It's not something that you explicitly find in some book, but I really need to improve that aspect since it has given me lots of trouble, and it's annoying because I do understand the actual physics material (in this case, Statics).

  5. Mar 29, 2013 #4


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    You should have studied these subjects in high school. In fact, I am rather puzzled that you are taking statics in what should be an honors high school physics course or basic college course in statics without having studied algebra or trigonometry.
  6. Mar 31, 2013 #5
    There's no need to be condescending or puzzled about me... I just asked kindly for your help my friend. All I'm saying is that I would like to refresh that stuff and if there's a source that focuses on it, that'd be awesome.

    Just for the record... after high school I did something else with my life (no, I was not a hippie, I became a commercial pilot and did that for 4 years) and now I'm at university and all this stuff got very rusty. I did study algebra and trig on high school (10 years ago) but probably it was not at a good level for this Statics course.

    You'd be surprised with how many people that just finished high school struggle with "basic" stuff.

    ANYWAY.... I'd appreciate the help if you can provide it, all I'm looking for is learn more.
    Thanks again for the help with the problem.

  7. Mar 31, 2013 #6


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    No disrespect was intended, but consider things from the helper's point of view. When someone posts a problem, the helper knows nothing about the OP's background or educational history unless the OP chooses to share. Oftentimes, an OP is trying to self-teach a subject and may not have covered subjects in his self-study which would normally have been encountered in school. The lack of adequate academic grounding may contribute to all or part of the difficulty the OP has with solving a particular problem.

    Now, in your case, since you have been out of school for an extended period and are trying to reenter academic study, a fairly extensive refresher course of study may be required. For the subjects of geometry and trigonometry, there are many sites online which can provide the basics or more advanced study in these and other areas of mathematics. I have found the math articles in Wikipedia to give a concentrated treatment of their subjects. By searching the web for other math sites, you will undoubtedly find others which may give you the right level of help.

    Paul's Online Math Notes has good articles for algebra, trig, and calculus, but is noticeably lacking in covering topics in plane geometry. TheMathPage I think can make up for what Paul's lacks in basic math.
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