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Homework Help: Force Of Friction

  1. Jan 10, 2012 #1
    1. The problem statement, all variables and given/known data

    A 1250 kg car traveling at 60.0 km/h comes to a sudden stop in 35 m. What is the coefficient of friction acting on the brakes?


    2. Relevant equations
    Fr= μN
    Fn= ma

    3. The attempt at a solution
    I'm stumped on how to figure out the acceleration of the car as they only give you the mass, distance, and final velocity. Can anybdoy help me? Thanksss!
  2. jcsd
  3. Jan 10, 2012 #2


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    Do you have a list of formulas for constant accelerated motion?
    There is one that does the job!
  4. Jan 10, 2012 #3
    no i wasnt given a list, sorry.
  5. Jan 10, 2012 #4


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    Staff Emeritus
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    Gold Member

    As Delphi51 said, you could use one of the kinematic equations.

    However, you can work it out as follows.

    Assuming uniform acceleration,you can easily determine the average velocity. (Do you know what the average velocity is during the time the car is braking?) Then from that you can find the time to go 35 meters. Then find the acceleration.
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