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Homework Help: Rotational Motion of a Cylinder

  1. Mar 5, 2009 #1
    1. The problem statement, all variables and given/known data

    A uniform 3.8-kg cylinder can rotate about an axis through its center at O. The forces applied are: F1 = 4.6 N, F2 = 6.2 N, F3 = 8.0 N, and F4 = 3.1 N. Also, R1 = 10.7 cm and R3 = 5.8 cm. Find the magnitude and direction (+: counterclockwise; -: clockwise) of the angular acceleration of the cylinder.

    F1 = 4.6N
    F2 = 6.2N
    F3 = 8.0N
    F4 = 3.1N

    R1 = .107M
    R2 = .107M
    R3 = .058M
    R4 = .107M

    I = .2033
    M= 3.8kg



    attachment.php?attachmentid=6485&d=1142284871.gif
    2. Relevant equations
    T = F * R
    ang accel = T/I
    I= 1/2MR^2


    3. The attempt at a solution
    *0 = omega since i dont have key
    T=Frsin0
    F1= 4.6*.107sin90 = .4922
    F2= 6.2*.107sin90 = -.6634
    F3= 8.0*.058sin90 = -.464
    F4= 0
    Fnet = -.6352

    -.6352/.2033= -3.124 rad/s^2
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 6, 2009 #2

    alphysicist

    User Avatar
    Homework Helper

    Hi shadowice,

    When you calculated the moment of inertia, I believe you forgot to square the radius.
     
  4. Mar 6, 2009 #3
    thnx dont know why i didnt double check that i almost always do
     
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