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Homework Help: Speed and accleration of a turntable

  1. Mar 4, 2008 #1
    1. The problem statement, all variables and given/known data

    An electric turntable 0.740m in diameter is rotating about a fixed axis with an initial angular velocity of 0.290rad/s . The angular acceleration is 0.900rad/s^2 .

    a) Compute the angular velocity after a time of 0.194s. - .465rev/s

    b) Through how many revolutions has the blade turned in this time interval? - .073rev

    c) What is the tangential speed of a point on the tip of the blade at time t = 0.194s ?

    d) What is the magnitude of the resultant acceleration of a point on the tip of the blade at time = 0.194 ?

    2. Relevant equations

    v = r[tex]\omega[/tex]

    arad = [tex]\omega[/tex]^2r

    atan = r[tex]\alpha[/tex]

    3. The attempt at a solution

    for part c)

    v = (.740/2)(.465) = .172m/s wrong

    for part d)

    arad = (.465)^2(.740/2) = .0800m/s^2

    atan = (.740/2)(.900) = .333m/s^2

    a = (.0800^2 + .333^2)^(1/2) = .342m/s^2 wrong

    I'm not sure what I'm doing wrong, any help is appreciated.
  2. jcsd
  3. Mar 5, 2008 #2
    For part C it seems as if you need to do is convert the revs to meters. To do this you need to know the circumference (which would be the distance "unrolled" after 1 revolution)
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