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Homework Help: 2 MCAT questions - friction

  1. Jan 6, 2010 #1
    1. The problem statement, all variables and given/known data

    1. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how far does the car slide?

    A. 50 m
    B. 100 m
    C. 200 m
    D. 400 m

    2. A car moving at 20 m/s brakes and slides to a stop. If the coefficient of kinetic friction between the pavement and the tires of the car is 0.1, how much time is needed for the car to come to a complete stop?

    A. 1 s
    B. 10 s
    C. 20 s
    D. 40 s


    2. Relevant equations

    U(k)mgcos0

    3. The attempt at a solution

    Well the answers for both are C, as the back of the book states. The problem is, I don't understand how you can figure out either the time or distance with the information given... can anyone shed some light?
     
  2. jcsd
  3. Jan 6, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

    Use energy conservation for the first one, the work done by friction is the change in kinetic energy.
     
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