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Homework Help: Height of ramp given normal force in circular loop

  1. Aug 21, 2011 #1
    1. The problem statement, all variables and given/known data
    The attachment shows the problem. The normal force at the top of the loop is 3 g's (as in g-force).

    2. Relevant equations
    PE = mgh
    KE = .5mv2
    Fc = [itex]\frac{mv2}{r}[/itex]
    PE + KE = PE' + KE'
    v = [itex]\sqrt{2gh}[/itex]

    3. The attempt at a solution
    The normal force would be: 30 * mass.

    Since he's at the top of the loop, the formula would be:
    Fnet = Fc = (mv2)/r = Fnormal + mg

    I have tried to cancel the mass out and to formulate a system of equations but I think I'm missing something. One formula I got is by setting PE equal to KE (for h, but only at the bottom before the skater goes up the loop):
    h = [itex]\frac{.5v2}{g}[/itex]

    I am starting to think that I need the radius/velocity. Any ideas?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    Attached Files:

  2. jcsd
  3. Aug 21, 2011 #2


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    Homework Helper

    Right so you can get v2 from this.

    Yes you will need the radius since v2 will be in terms of the radius 'r'.

    You are also correct in that h = ½v2/g, so you can use the v2 you found above here.
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