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Math Help - Velocity story problem

  1. #1
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    Velocity story problem

    A police car is traveling at a velocity of 19.0 m/s due north, when a car zooms by at a constant velocity of 42.0 m/s due north. After a reaction time of 0.800 s the policeman begins to pursue the speeder with an acceleration of 5.00 m/s2. Including the reaction time, how long does it take for the police car to catch up with the speeder?
    Given: Vpolice = 19.0 m/s, Vcar = 42.0 m/s , Acc.police = 5.00m/s, t = unknown

    I need help setting up this problem.
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  2. #2
    Newbie Firstone's Avatar
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    Hmm i haven't done these kinds of questions for awhile, so this may be wrong.
    Vpolice * t + Apolice * t^2 = Vcar * t + Vcar * 0.8
    Put it into the form of a quadratic, then solve for x, and it should be the positive number I think.
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  3. #3
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    I did what u said and got:

    19.00t + 5.00t^2 = 42t + 42*08

    5t^2 - 23t - 33.6 = 0

    X= 5.7655, X= -1.1655

    so the answer is 5.77 ?
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  4. #4
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    t is the time of acceleration for the police car

    (19 m/s)(t + 0.8 s) + (1/2)(5 m/s^2)t^2 = (42 m/s)(t + 0.8 s)

    solution to the problem is (t + 0.8 s)
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  5. #5
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    got it thank you
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