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Homework Help: Coefficients of Static Friction

  1. May 22, 2007 #1
    1. A 13,500 N car traveling at 50.0 km/h rounds a curve of radious 2.00m x 10 ^ 2.
    Find the following:
    A. the centripetal acceleration of the car (.965 m/s[2])
    B. The centripetal force (13,500 N) C
    C. The minimum coefficient of static friction between the tires and the road that will allow the car to round the curve safely.

    I need help on question C. I have found the answers to a and b already and put them in parentheses. I know that the equation for the coefficient of friction is u=f max/ f[normal]. I know that the f max is the maximum amount of force you can exert on an object before it will begin to start moving. I am having trouble on where to start to find the fs max. Your help is greatly appreciated.
  2. jcsd
  3. May 22, 2007 #2
    B. The centripetal force is
    Fc = m * ac
    It is not 13500 N.
    C. You can just use the simple formula for that
    u = Ff/Fn
    u = coefficient of friction
    Ff = friction force
    The force of centripetal acceleration is equal to the force of friction. Since the car is not skidding.
    The maximum value Ff can have is the maximum value of Fc.
    You know Fc and Fn so... :)
  4. May 22, 2007 #3
    For the mass of the car, do i use 13,500 N or do i break the newtons down into kg * m/s[2] and solve for kg?
  5. May 22, 2007 #4
    Mass is measured in kilograms.
    Weight is measured in Newtons.
    Fg = m * g
  6. May 22, 2007 #5
    Thanks very much husky88. I calculated the Fc to be 1,328 N.and then i took that and divided it by 13,500 N to get a u of .10
  7. May 22, 2007 #6
    :approve: There you go.
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