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Homework Help: Angular Speed of a drive train

  1. Mar 15, 2008 #1
    1. The figure below shows the drive train of a bicycle that has wheels 67.3 cm in diameter and pedal cranks 17.5 cm long. The cyclist pedals at a steady angular rate of 76.5 rev/min. The chain engages with a front sprocket 15.2 cm in diameter and a rear sprocket 7.25 cm in diameter.

    2. v = r*w

    3. First I tried to find the velocity of the rear sprocket.

    radius of rear sprocket is 0.0363 m
    angular speed of pedaling is 8.01 rad/s

    v = 0.0363 * 8.01
    v = .291 m/s

    radius of wheels is 0.337 m

    So I used the velocity of the rear sprocket to calculate the angular speed of the wheel

    w = .291/.337
    w = .864 rad/s

    I am using WebAssign, and when I entered this answer, it said my answer differed by orders of magnitude. Any help would be greatly appreciated, since I only have one more shot at getting the answer right. Thanks


  2. jcsd
  3. Mar 15, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Can you post the figure?
  4. Mar 15, 2008 #3

    there u go
  5. Mar 15, 2008 #4

    Doc Al

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    Staff: Mentor

    But you used the angular speed of the front sprocket, not the rear sprocket.

    Hint: Since they are connected by a chain, the tangential velocity (v, not angular speed) of each sprocket is the same.
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