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Homework Help: Compact Disc Problem

  1. Nov 29, 2007 #1
    1. The problem statement, all variables and given/known data

    The inner and outer radii of a compact disc are 25 mm and 58 mm. As the disc spins inside a CD player, the track is scanned at a constant linear speed of 1.25m/s. The maximum playing time of a CD is 74.0 min. What is the average angular acceleration of a maximum-duration CD during its 74.0-min playing time? Take the direction of rotation of the disc to be positive.

    2. Relevant equations

    angular acceleration=rw^2

    3. The attempt at a solution
    I tried to integrate wr somehow, but w is not constant.
  2. jcsd
  3. Nov 29, 2007 #2


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    Homework Helper
    Gold Member

    You don't need to integrate.

    First of all, [tex]\omega[/tex], is the angular frequency. Your second formula is wrong. It should read;

    [tex]a=r\omega^2[/tex] where a is the linear acceleration.

    Either way, all you should need to solve this is the first formula.

    You know that v=1.25m/s.

    Can you use this, and your first formula to find the angular acceleration? If so, it should just be an algebra problem to find the average angular acceleration.
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