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Homework Help: Circular Velocity of car

  1. Sep 26, 2011 #1
    1. The problem statement, all variables and given/known data
    Disturbed by speeding cars outside his workplace, Nobel laureate Arthur Holly Compton designed a speed bump (called the "Holly hump") and had it installed. Suppose a 1 800-kg car passes over a hump in a roadway that follows the arc of a circle of radius 21.4 m as in the figure below.

    (a) If the car travels at 28.5 km/h what force does the road exert on the car as the car passes the highest point of the hump?


    2. Relevant equations

    Normal Force - Weight = [mass(velocity^2)]/radius


    3. The attempt at a solution

    I used the equation above and converted the velocity to m/s which i got 7.9166

    Then basically plug n chug.

    My final answer was 22911.6 (sig figs doesn't matter here)

    But when I submitted my answer it says my answer is off more than %10 of the actual answer.

    Any suggestions?
     
  2. jcsd
  3. Sep 26, 2011 #2
    Hi,
    You should've included the centrifugle force, in your reference frame, in the following manner:
    [itex]
    \large
    N-mg+F_c = 0 \Longrightarrow N = mg-\frac{mv^2}{R}
    [/itex]
    Try it,
    Daniel
     
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