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Homework Help: Converting Linear Equation to Angular Equation

  1. Oct 27, 2005 #1


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    Can anyone help me convert this linear equation to angular terms?

    mx'' + f*sin(x') + kx = 0

    x'' = x double dot
    x' = x dot

    Im having trouble find info on changing this.
  2. jcsd
  3. Oct 27, 2005 #2


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    Well so far I have:

    IΘ'' + (g/L)Θ' + ? = 0

    I used the small angles approximation which got rid of the sin(Θ').

    Can anyone help me turn the kx itno angular terms?
    I know x goes to Θ but not sure about the spring constant.
  4. Oct 27, 2005 #3


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    I just found something.

    Im thinking k = ω^2*m

    So that makes this ω^2*m*Θ

    and m = I

    so my final equation is

    IΘ'' + (g/L)Θ' + ω^2IΘ = 0

    Does this look right?
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