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Homework Help: Plug in time to find the acceleration

  1. May 27, 2008 #1
    Heres the problem Im working on...

    http://img502.imageshack.us/img502/1613/rotut5.jpg [Broken]

    Im trying to figure how to plug in time to find the acceleration....

    I found the first acceleration of 100mm/s^2......but im not sure how to get the others...

    I was using the formula

    [tex] a_{t} = r\theta [/tex]

    [tex] a_{n} = r\omega^2 [/tex]
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. May 27, 2008 #2

    Doc Al

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    Staff: Mentor

    That first equation should be:

    [tex] a_{t} = r\alpha [/tex]

    How can you find the angular speed at each of those times?
  4. May 27, 2008 #3
    at time = 0 I was able to do

    [tex] a_{t} = r\omega = 9(.200)(.5) = .100 = 100mm/s^2 [/tex]

    and that is correct for the first answer....

    but for the other times I wasnt sure...
  5. May 27, 2008 #4
    ok I figured it out for time at 2...and its the same for each time....its just

    [tex] a_{t} = r\alpha = (.200)(.5) = .100 [/tex]

    [tex] \omega = \omega_{o} + \alpha(t) [/tex]

    [tex] \omega = .5 rad/s[/tex]

    [tex] a_{n} = r\omega^2 = (.200)(.5)^2 = .050[/tex]

    [tex]A = \sqrt{a_{t}^2+a_{n}^2} = 111.8 mm/s^2[/tex]
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