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Homework Help: Zero Normal force during uniform circular motion?

  1. Jun 23, 2011 #1
    I am learning uniform circular motion and the question says: A child on a sled comes flying over the crest of a small hill. His sled does not leave the ground but he feels the normal force between his chest and the sled decrease as he goes over the hill. Explain.

    Now, I know that normal force decreases at the crest of the hill as there is downward centripetal force. But how exactly does it 'feel' when the normal force decreases/ goes to zero? Do you become air-borne? Shouldn't the sled be penetrating the hill since the weight is now greater than normal force?

    Confused student.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jun 23, 2011 #2


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    welcome to pf!

    hi soominds! welcome to pf! :smile:

    there is no such thing as https://www.physicsforums.com/library.php?do=view_item&itemid=529"

    there is https://www.physicsforums.com/library.php?do=view_item&itemid=84" (in the reference frame of the child)

    and there is https://www.physicsforums.com/library.php?do=view_item&itemid=27" (in the stationary reference frame)

    which frame does your professor want you to use?​
    Last edited by a moderator: Apr 26, 2017
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