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Vector Force - Supporting Vs. Hanging

  1. Nov 2, 2015 #1
    I have only a very basic understanding of vector forces in the context of hanging loads - for example, a weighted object anchored from two points, the internal angle between the two lines from those points to the load determining the actual force each line must support.

    What I don't know is if the same vector forces apply if you essentially invert that system - that is, a single base with two support arms leaving it at an angle and supporting a single load (e.g. a barbell held overhead with a wide grip).

    In a typical snatch-width grip, a lifter will have about a 75-degree angle between the arms. If this were a hanging system, this would mean each arm were supporting about 63% of the weight. Does this hold true in the opposite direction?

  2. jcsd
  3. Nov 2, 2015 #2


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    The free body vector diagram is not the same as the original diagram turned upside down. But the features relevant to your specific question are the same.
  4. Nov 2, 2015 #3


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    As far as I can see, the answer to your question is Yes. It may be difficult to produce two situations in practice that are clearly mirror images of each other but it's right in principle.

    You may be interested to see what this link has to say about the idea. The Spanish architect Gaudi created a number of architectural designs for systems of arches, by making 'upside down' models, using chains with weights hanging on them. There are many examples of his work to be seen in Barcelona and there is a museum which shows models of his technique. nSo the idea certainly has legs.
  5. Nov 2, 2015 #4
    Thank you!
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