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General loop the loop problem

  1. Mar 8, 2015 #1
    1. The problem statement, all variables and given/known data
    In the normal loop the loop problem involving rotational energy where the marble goes down the hill and goes through a loop the loop, it asks for the minimum height of the hill to keep the marble on the track.

    2. Relevant equations
    But why does the normal force have to equal 0?
    3. The attempt at a solution
    I just dont know. How do we factor the idea that the marble doesnt fall off into the problem?
  2. jcsd
  3. Mar 8, 2015 #2


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    The normal force cannot be negative, agreed?
    You are looking for the minimum initial height for it to stay on track. If the normal force at the top were greater than zero then a lower initial height could have been used.
    Zero is the only remaining possibility.
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