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Homework Help: Lever with offset pivot problem

  1. Nov 1, 2011 #1
    1. The problem statement, all variables and given/known data

    I have a situation a shown in the diagram below. A lever with a gas compression spring opposing it's turning. I want to find the force acting on the spring, F1, for a given inital force @ F0.

    [PLAIN]http://img18.imageshack.us/img18/9830/lever01.png [Broken]

    2. Relevant equations

    3. The attempt at a solution

    I don't think this is a trivial lever problem but I may be wrong???
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Nov 1, 2011 #2


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    Welcome to PF.

    You're right. It's not trivial.

    How do you plan to solve it?
  4. Nov 2, 2011 #3
    I have reduced it to a static problem and am looking at the initial configuration as drawn above, before any movement.

    In this situation I believe that F1 can be worked out by introducing an imaginary lever, as shown below and balancing the moments i.e.

    (F0)(5x) = (F1)(y)

    where y can be found by trigonometry using similar triangles.

    However if we revert the problem back to a dynamic one, the length y will change as the system turn and the spring compresses, so for a constant force F0, F1 will vary. However I think you could plot this out over a certain turning angle, by just selecting a range of angles and calculating y for that configuration and thus F1.

    I appreciate any comments :smile:

    [PLAIN]http://img839.imageshack.us/img839/8334/lever02.png [Broken]
    Last edited by a moderator: May 5, 2017
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