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Homework Help: Harmonic Motion and uniform disk of mass

  1. Aug 11, 2016 #1
    1. The problem statement, all variables and given/known data
    A uniform disk of mass m and radius R lies in a vertical plane and is pivoted about a point a distance ℓcm from its center of mass in (Figure 1) . When given a small rotational displacement about the pivot, the disk undergoes simple harmonic motion.

    Determine the period of this motion. Use the notation lcm for the distance ℓcm.
    Express your answer in terms of π, acceleration due to gravity g, some or all of the variables m, R, and lcm.


    2. Relevant equations
    I = ½m*R² + m*L²

    T = 2π*√[I/(m*g*L)]

    3. The attempt at a solution

    T = 2π*√[(R² + *L² )/(g)] was wrong
  2. jcsd
  3. Aug 11, 2016 #2


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    Science Advisor
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    Gold Member

    That answer does not follow from your initial equations. I notice an asterisk to the left of the L. Did you omit something?
    Please post your working.
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