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Homework Help: Rotational kinematics

  1. May 28, 2016 #1
    1. The problem statement, all variables and given/known data
    A wheel of diameter 45.0 cm starts from rest and rotates with a constant angular acceleration of 2.50 rad/s2 . At the instant the wheel has completed its second revolution, compute the radial acceleration of a point on the rim in two ways.

    1 Using the relationship aredial2r.

    2 From the relationship aredial=v2/r.

    2. Relevant equations
    rotational kinematics

    3. The attempt at a solution

    α= 2.5
    it says second rotation so θ= 2π*2 = 12.57

    θ = ωt + ½ α t2
    12.57 = ½ 2.5 t2
    t= 3.171

    ω = ω + α t
    ω = 2.5 (3.171)
    ω = 7.927

    a = 7.9272 * 22.5 = 1413.716694

    2 should be the same answer since the equations are equal
    why is my answer wrong?
  2. jcsd
  3. May 28, 2016 #2


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    Science Advisor
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    Gold Member

    Is the diameter of the wheel ##45m## or ##45cm##?
  4. May 28, 2016 #3
    got it, there was my mistake, thank you
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