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Slider on rod

  1. Feb 18, 2007 #1
    1. The problem statement, all variables and given/known data
    k = 40 N/m
    mass of slider = 200 g
    EDIT r = 0.3 m
    Hoop is VERTICAL, undeformed length of the spring is when spring is in position AB, slider NOT attached to spring.

    Find smallest value for theta such that the slider will pass through D and reach A (see picture).

    2. Relevant equations

    s = r*theta
    1/2 k * x^2
    1/2 mv^2

    3. The attempt at a solution

    I set up the initial and final energy equations but couldn't figure out how to solve them. =P

    Denoting @ as theta:

    mgr(1-cos(@)) + 1/2*k(r@)^2 = mg*2r

    After plugging in numbers and rearranging, I found:

    mgcos(@) + 0.0018277@^2 = 1.962

    I don't know how to solve for @ in that equation. Also, in the spring term of 1/2kx^2, I replaced x by r@ (s = r@) and multiplied @ by pi/180 to convert to radians for that term.

    Attached Files:

    Last edited: Feb 18, 2007
  2. jcsd
  3. Feb 18, 2007 #2


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    Homework Helper

    Until you post a clearar diagram, I doubt anyone will be able to entirely check your equations.
  4. Feb 18, 2007 #3
    That's the diagram in my book really...It's a vertical circle with a slider and a spring attached to point A (slider NOT attached to spring)

    And my equation is wrong I discovered, but have NO clue what the right one is.
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