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Question about rotational energy.

  1. Nov 27, 2009 #1
    1. The problem statement, all variables and given/known data
    Five objects of equal mass are shown below together with the axis about which they are rotating. Select the objects in order of increasing rotational energy

    Solid Sphere, about any diameter, with R = 3 m and ω=5 rad/s

    Thin rod, about axis through center, perpendicular to the length with l = 8 m and ω=6 rad/s

    Solid Cylinder, about cylinder axis with R = 3 m and ω=5 rad/s

    Thin Spherical shell, about any diameter, with R = 2 m and ω=7 rad/s

    Thin cylindrical shell, about cylinder axis with R = 1 m and ω=7 rad/s

    2. Relevant equations


    3. The attempt at a solution

    Most of these have no mass or moment of intertia included and im not sure how to deal with that.
  2. jcsd
  3. Nov 27, 2009 #2


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    You are supposed to calculate the moments of inertia first. Your textbook must have a table where these are listed. Note that all the masses are the same, therefore you can rank the energies because they will always be

    E = (some number)*m
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