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Homework Help: What is the drill's angular acceleration?

  1. Feb 5, 2010 #1
    1. The problem statement, all variables and given/known data

    A high-speed drill rotating ccw at 2200rpm comes to a halt in 2.80 s. What is the drill's angular acceleration?

    2. Relevant equations

    (where w = angular velocity)
    w = 2╥/T
    v = wr
    a = v^2/r
    a = w^2*r

    3. The attempt at a solution

    I start by calculating w. So first I took it to rev per second and then second per revolution which came to be 0.027 seconds per revolution. So w = 2╥/0.027 = 232.71 radians. Now I'm stuck because I don't have r (radius). I've tried going backwards to get r from v, but to no success since v depends in r as r depends in v. Every equation relating to acceleration seems to need r but I don't see how I can get it. Any ideas would be appreciated. Thanks.
  2. jcsd
  3. Feb 5, 2010 #2


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    Homework Helper

    you don't need radius or linear velocity.

    [tex]\alpha = \frac{\omega_f - \omega_i}{t}[/tex]
  4. Feb 5, 2010 #3
    Thank you. I realized after you posted that equation that it was a nonuniform circular motion problem, I was going about it the wrong way.
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