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Kinetic or Static coefficient?

  1. Oct 31, 2006 #1
    I have this question on my homework, but I think maybe all the answers are wrong. I figure it should be C since the road is icy, but shouldn't I be using the coefficient of static friction instead of kinetic? any help is appreciated. thanks.


    As a car skids with its wheels locked trying to stop on a road
    covered with ice and snow,
    the force of friction between the icy road and the tires will
    usually be: (Please note that
    "normal" and "perpendicular" have the same meaning)

    a. greater than the normal force of the road times the coefficient
    of static friction
    b. equal to the normal force of the road times the coefficient of
    static friction
    c. less than the normal force of the road times the coefficient of
    kinetic friction
    d. greater than the normal force of the road times the coefficient
    of kinetic friction
    e. equal to the normal force of the road times the coefficient of
    kinetic friction.
     
  2. jcsd
  3. Oct 31, 2006 #2
    thje way the question is worded means there is friction between the tires and the icy road regardless of the ice

    how do you calculate force of friction?? Is there any OTHER way that you know of?
     
  4. Oct 31, 2006 #3

    Office_Shredder

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    Staff Emeritus
    Science Advisor
    Gold Member

    Let's see.... the car is sliding along the ice, so it's actually moving. Which friction would you use if an object is sliding a surface?
     
  5. Oct 31, 2006 #4
    This is a case of kinetic friction.
    The static friction only applies to a rotating wheel (the friction between the wheel and the road allow the wheel to rotate); since it is only skidding, kinetic friction is the right one.
     
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