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AP Physics problem

  1. Sep 13, 2010 #1
    1. The problem statement, all variables and given/known data
    A car with a speed of 40.0 km/h approaches the bottom of an icy hill. The hill has an angle of inclination of 10.5 degrees. The driver applies the brakes, which makes the car skid up the hill. If the coefficient of kinetic friction between the ice and the tires if 0.153, how high, measured along the incline, is the car on the hill when it comes to rest?

    vi=40.0km/h=11.1m/s^2
    theta=10.5 degrees
    fk=0.153


    2. Relevant equations


    3. The attempt at a solution
    -a=g(sinθ-ϥkcosϴ)
    a=-.31m/s^2

    vf^2-Vi^2/2(a)
    =198.7m
     
  2. jcsd
  3. Sep 13, 2010 #2
    -a=g(sinθ-ϥkcosϴ)
    shouldn't it be:
    a = -g(sinθ+fkcosθ)?
    both forces points in opposite direction of initial velocity. So if you choose initial velocity to be (+) direction along hill, then acceleration due friction is negative and also due gravity is negative.
     
  4. Sep 13, 2010 #3
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