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Homework Help: Banked Curve Question

  1. Jun 4, 2010 #1
    1. The problem statement, all variables and given/known data
    A curve of radius 68m is banked for a design speed of 85km/h. If the coefficient of static friction is 0.30 (wet pavement), at what range of speeds can a car safely make the curve?

    2. Relevant equations

    1) FNsin(theta) = m*v2/r
    2) FNcos(theta) - mg = 0
    3) tan(theta) = v2/rg

    3. The attempt at a solution

    I used the third equation to find (theta) which is 39.9o
    but I can't find out how to find Ffr or the range of velocity
    I understand that when the car goes slow the frictional force faces up the banked curve and when it goes fast the friction goes down the banked curve but I can't figure out how to solve the question.
  2. jcsd
  3. Jun 4, 2010 #2


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    Science Advisor
    Homework Helper

    Hi hanlon! :smile:

    (have a theta: θ and a mu: µ :wink:)
    When the car is at its fastest safe speed, the friction force will be µsFN, = 0.3FN.

    So rewrite 1) and 2) to include the friction …

    what do you get? :smile:
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