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Hanging a uniform bar

  1. Jan 10, 2015 #1

    pitbull

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    1. The problem statement, all variables and given/known data
    Given a uniform bar of length L, which point should you hang it from (between 0 and L) so that you get maximum frequency for small oscillations?

    2. Relevant equations
    ...

    3. The attempt at a solution
    It seems like a basic problem, but I don´t know how to start. Could you guys give me some clues to start it?
     
  2. jcsd
  3. Jan 10, 2015 #2

    haruspex

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    First, draw a diagram of the bar in some position and find the forces on it. If you can't post diagrams readably then describe it as well as you can.
     
  4. Jan 10, 2015 #3

    gneill

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    Look up "physical pendulum" and refresh your memory about rotational motion, moments of inertia, and so on.
     
  5. Jan 10, 2015 #4

    pitbull

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    Would it be easy to solve it using Lagrange method?
     
  6. Jan 10, 2015 #5

    gneill

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    I'll admit that I haven't thought about that. I suppose that you could write the Lagrangian for the system and work from there. Give it a go and see where it takes you.

    Personally I see it as a physical pendulum problem for which a formula for the period is well known. All you need to do is account for different pivot locations (a well known theorem related moments of inertia is involved) and seek a minimum.
     
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