Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Friction cars racing

  1. Feb 16, 2009 #1
    1. The problem statement, all variables and given/known data
    Two cars are going to begin at rest and race 200 meters to a stoplight. One driver sneaks over and puts oil on the other car's tires, which reduces it coefficient of friction to .07. Assuming the first car does not slip then by how much distance will it win?

    2. Relevant equations
    Ff = μ(Fn)
    a = μ(9.8)
    Vf^2 = Vi^2 + 2a * x
    Static coefficient of friction of rubber on concrete = 1.0
    Kinetic coeff. of friction of rubber on concrete = 0.8

    3. The attempt at a solution
    1st car:
    Vf^2 = 2(.8*9.8)200
    vf = 39.6 m/s

    2nd car:
    a = .07(9.8)
    a = .686 m/s^2

    vf^2 = 2(.686)
    vf = 1.2 m/s

    Not sure what to do now.
  2. jcsd
  3. Feb 16, 2009 #2


    User Avatar
    Homework Helper

    All things being equal for the first car then I'd say it's acceleration would be .07 of the second.

    So for the unslicked car 200 = 1/2a*T2

    The slicked car would only have gone only .07 (200) = 14 m in the same time.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook