Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Science Advisor
    Homework Helper

    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook