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Homework Help: Force and newtons law of motion

  1. May 5, 2010 #1
    1. The problem statement, all variables and given/known data
    your car rolls on a level street at 50km/h. the coefficient of kinetic friction is 0.023. how far will the car go before stopping. (no breaking.)


    2. Relevant equations



    3. The attempt at a solution
    F_fric=0.226m
    F_a=(-1250/s)*m
    i need to make F_a-F_fric equal to something to solve for s, the m's will cancel. I have no idea what it will equal since its not in equilibrium......
     
  2. jcsd
  3. May 5, 2010 #2

    tiny-tim

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    hi pat666! :wink:

    use work done and the work-energy theorem :smile:
     
  4. May 5, 2010 #3
    kk ill give that a whirl and tell you if i still cant do it... thanks
     
  5. May 5, 2010 #4
    Hey, i still cant get this i tried finding the net work which i got -1250m J and then W=F/x with F=(-1250m)/x-0.226m. i got the acceleration (for F=ma) using kinematic equations.???????????????
     
  6. May 5, 2010 #5

    tiny-tim

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    Sorry, I don't understand any of that. :redface:

    What is the energy? what is the force ?

    If the distance is d, what is the work done ?
     
  7. May 5, 2010 #6
    I just found the net work using 1/2mv^2-1/2mu^2. then i used W=F/x, to find the Force i just found the Force from friction and the "applied force". I might be doing something completely wrong, could you give me some more detailed instructions please.
     
  8. May 5, 2010 #7

    ideasrule

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    It's W=Fx, not W=F/x. Also, there's no applied force; the force on the car is just the force of friction.
     
  9. May 5, 2010 #8
    ok thats where i screwed up. thanks.......
     
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