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Homework Help: Angular acceleration, is my method correct?

  1. May 2, 2009 #1
    1. The problem statement, all variables and given/known data

    A Pulley has mass M=4 kg and radius R=0.4 m. Assume that it is a uniform solid disk so that its moment of inertia is I= .5MR^2. A massless cord is wrapped around it and a tension force Ft is applied. The pulley starts from rest. After the tension force has been applied for 6 seconds, the angular speed has reached T=60 rads/s.

    2. Relevant equations

    a.) What is the pulley's angular acceleration?

    b.) What is the linear (tangential) acceleration of a point on the rim of the pulley?

    3. The attempt at a solution

    a.) V=(2*pi*R)/T
    V= .418 m/s

    w=1.045 rads/sec

    angular acceleration= w2-w1/t2-t1
    = (1.045-0)/(6-0)
    = .15 rads/s^2

    b.) Tangential acceleration= r*alpha
    =.o2 m/s^2

    Can anyone please tell me if this is correct?? Thank you thank you!
  2. jcsd
  3. May 2, 2009 #2


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    Homework Helper

    Consider that it is uniform acceleration and

    ω = a*t

    a) is given simply by

    60 = a*6 or a = 10 rad/sec2

    b) would be determined by the same method you used.
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