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Homework Help: Need help with finding the speed

  1. Jun 3, 2008 #1
    [SOLVED] Need help with finding the speed

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

    A car goes around a curved stretch of flat roadway of radius R = 94.0 m. The magnitudes of the horizontal and vertical components of force the car exerts on a securely seated passenger are, respectively, X = 215.0 N and Y = 510.0 N.

    At what speed is the car travelling?

    i have no idea how to solve this.

    2. Relevant equations
    not quite sure

    3. The attempt at a solution

    :(
     
  2. jcsd
  3. Jun 3, 2008 #2
    a= v^2 / r
    v = SQRT(ar)
    Y=F =510N= mg , m= 510/9.8=52.04
    X=F= 215N=ma , a= 215/52.04=4.13
    v= SQRT(4.13*94)
     
    Last edited: Jun 3, 2008
  4. Jun 3, 2008 #3

    tiny-tim

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    Hi hayowazzup! :smile:

    Yes that looks good …

    though I'd have shortened it by writing v = √(rg 215/510) …

    then you can do all the calculation in one go. :smile:
     
  5. Jun 3, 2008 #4
    umm i got 19.13m/s
    Convert it now km/h, 19.13 * (1000/(60*60))= 5.315km/h
    but the answer in the book is 68.9km/h
     
  6. Jun 4, 2008 #5

    alphysicist

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    hayowazzup,

    I believe your conversion factor is upside down; you divide by 1000 to convert from meters to km, and you multiply by 3600 to convert from (1/s) to (1/hours).
     
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