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Homework Help: Angular motion of a weather vane. How fast is it spinning after impact (rpm)?

  1. Dec 2, 2011 #1
    1. The problem statement, all variables and given/known data
    A weather vane sits quietly on the roof of a barn on a calm winter's day. It has a length of x, is pole-shaped with mass M, and rotates frictionlessly about its center. But just now it is still.

    Suddenly Justin throws a snowball of mass m at speed v that hits it a distance r from one end. How fast is the vane spinning (in rpm) after the impact?

    2. Relevant equations

    3. The attempt at a solution
    I am not really sure how to approach and set up this problem. please help!
  2. jcsd
  3. Dec 2, 2011 #2


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    Staff: Mentor

    We don't know if the snowball hits and sticks to the rod in part or in whole, or if it shatters, or if it bounces (elastically). So it's not clear how we should treat the collision.

    Whatever the answer to the above is, it looks like conservation of angular momentum will play a key role.
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