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Disk acceleration physics homework

  1. Nov 13, 2009 #1
    1. The problem statement, all variables and given/known data

    A force of 2.2N acts tangentially to the rim of a solid 52kg disk, with a radius of 32cm. How long does it take to accelerate the disk, rotating about an axis though it's center and perpendicular to it's plane, from rest to 210 rev/min?

    2. Relevant equations
    Idisk=.5mr^2
    T=I (wierd fish symbol)
    fish symbol = Wf - Wi
    t


    3. The attempt at a solution
    i dont know how to find the wierd fish symbol.. one because i dont know what it stands for and two. i need that inorder to find time..

    HELP PLEASE!?
     
  2. jcsd
  3. Nov 13, 2009 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Welcome to PF.

    The wierd fish symbol is the greek letter alpha: [itex]\alpha[/itex] which means angular acceleration and has units of radians/time^2. The relationship between acceleration (distance/time^2) and [itex]\alpha[/itex] for a point rotating about a centre of rotation located at a distance r away is: [itex]\alpha = a/r[/itex].

    The relationship between torque and angular acceleration for a rigid object is:

    [tex]\tau = I\alpha[/tex]

    In order to answer this question, you will have to understand what that equation means.

    AM
     
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