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Help: Applied Force Formula(?)

  1. Apr 13, 2013 #1
    1. The problem statement, all variables and given/known data
    A 900kg car is moving on a level road at 80km/h. If the brakes are applied, what is the distance it will take to stop if the coefficient of kinetic friction between the tires and the road is 0.45.

    2. Relevant equations
    Really basic Kinematics and Forces(grade 11 level)

    3. The attempt at a solution
    I need help finding the formula for the Force applied. I find it really hard because I am not sure if the velocity is constant or not. I don't really know how to explain my attempt to solve it. I tried using D=vt but I can't find time without acceleration; without acceleration I am not able to find distance, etc.

    How would you solve this kind of problem? I tried to google for the formula but I can't seem to find any that will be suitable for this problem.

    Help would be very much appreciated.
  2. jcsd
  3. Apr 13, 2013 #2


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    Hello, Whatabootme. Welcome to PF.

    The force that's stopping the car is the force of friction. Do you know how to calculate the force of friction using the value of the coefficient of friction?
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