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Rotation Problem

  1. Mar 22, 2009 #1
    1. The problem statement, all variables and given/known data
    The wheel in Fig. 10-29 has eight equally spaced spokes and a radius of 30 cm. It is mounted on a fixed axle and is spinning at 3.6 rev/s. You want to shoot a 26-cm-long arrow parallel to this axle and through the wheel without hitting any of the spokes. Assume that the arrow and the spokes are very thin. What minimum speed must the arrow have?

    2. Relevant equations

    3. The attempt at a solution
    Okay so first i wrote down my givens.
    I found the angle between the spokes to be 45 or pi/4 radians.

    I did the 3.6rev/s time 2pi rad/rev which equals 7.2pi radians/s. That would be the angular velocity.
    I did pi/4 radians divided by 7.2 pi radians/s which equals 0.03472s for time.
    Now, I'm kinda stuck.
    Any help would be grateful. Thankyou!!
  2. jcsd
  3. Mar 22, 2009 #2


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    Gold Member

    You should see that the arrow only has 0.034s to travel 26 cm...
  4. Mar 22, 2009 #3
    heh.. i feel kinda stupid now...

    thank you for the help agh.. it was so obvious i didn't see it >.<
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