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Homework Help: How to find coefficient of friction?

  1. Nov 12, 2007 #1
    If a driver traveling down an 8% grade hill slams down the brakes of his car and skids 30 meters, what is the coefficient of friction ( assuming he was traveling at 25 MPH or more)?

    Appreciate your help asap.
  2. jcsd
  3. Nov 12, 2007 #2
    you use the acceleration due to gravity and say that the friction overcomes that by ___ amount
    Last edited: Nov 12, 2007
  4. Nov 12, 2007 #3
    What is 8% gradient in degrees?
  5. Nov 12, 2007 #4
    is Coefficient of friction tan(slope in degrees) ?
  6. Nov 12, 2007 #5
    i believe that 8% is the tangent of the angle. the coefficient of friction is mu, and for most cars should be between .6 and .8
  7. Nov 13, 2007 #6

    Doc Al

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    Staff: Mentor

    Assemble the usual suspects: Draw a diagram showing all the forces acting on the car. Apply Newton's 2nd law to relate the net force to the acceleration. Use kinematics or work/energy to compute the acceleration. (Pick a specific speed: convert 25 mph to m/s.)
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