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Homework Help: Angular Acceleration/ Find angle in period - PLEASE help!

  1. Nov 7, 2005 #1
    Angular Acceleration/ Find angle in period -- PLEASE help!

    I'm having trouble with part "B" please help.

    A.)A dentist's drill starts from rest. After 4.95 s
    of constant angular acceleration, it turns at a
    rate of 28600 rev/min.
    Find the drill's angular acceleration. An-
    swer in units of rad/s^2.

    B.)Find the angle through which the drill rotates
    during this period. Answer in units of rad.

    A.) [(28600*2pi)/60]/4.95 = 605.047 rad/s^2

    B.) [(28600*2pi)/60] * 4.95 = 14825 rad. (but this is not the right answer?)

    Am I using the wrong formula? Any help appreciated.
  2. jcsd
  3. Nov 7, 2005 #2

    Doc Al

    User Avatar

    Staff: Mentor

    This assumes that the speed is constant at (28600*2pi)/60 rad/s. But the speed is not constant; the drill starts from rest and accelerates.
  4. Nov 7, 2005 #3
    Thanks so much. Didn't realize that. So it's theta = .5 (605.047)(4.95^2)

    = 7412.58 radians.

    Thanks again. :)
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