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Ricky Bobby?

  1. Feb 27, 2009 #1
    Ricky Bobby??

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

    Ricky Bobby jumps into his 1003kg pick up and heads out at 69.2mi/h. It's night and he notices too late the warning sign that the bridge is out. He slams on the brakes and skids for 45.2(kinetic friction=0.78)before hitting the long massive coil spring that is rigidly mounted onto the barricade. In addition to his skidding tires, the spring brings him to a stop. The spring constant is 3.57 x 10^4 N/m. how far does he travel after making contact with spring???

    2. Relevant equations
    1/2mv^2+1/2Kx^2=1/2mv^2+1/2kx^2 ?????????????????// im not sure if this is the right equation i dont think it is ive looked everywhere in my book to find a relevent equation i was wondering if anyone can point me towards the right equation please

    3. The attempt at a solution

    refer to (b)2.
  2. jcsd
  3. Feb 28, 2009 #2


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    Hi ldbaseball16! :smile:

    Is that 45.2 feet?

    This is an energy problem …

    so yes, that equation is right, but you also need to use the work-energy theorem … work done by friction = loss of mechanical energy :wink:
  4. Feb 28, 2009 #3
    Re: Ricky Bobby??

    ok Wnet=(1/2)mv^2-(1/2)mv^2 this is the work energy theorem but on the other equation i have to apply the kinetic friction to 45.2m???? right and once i find the conservation of mechanical energy what do i do with that number???? how do i apply it to the work-energy theorem???
    Last edited: Feb 28, 2009
  5. Feb 28, 2009 #4


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    uhh? :confused: too cryptic :redface:

    just do it! :rolleyes:
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