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Homework Help: Police Question .

  1. Sep 12, 2006 #1
    Police Question.....

    Question:

    A speeder passes a parked police car at 30.0 m/s. The police car starts from rest with a uniform acceleration of 2.44 m/s^2.

    a) How much time passes before the speeder is overtaken my the police car? Ans: 24.6 s

    b) How far does the speeder get before being overtaken by the police car?
    Ans: 738 m

    My Questions/Work:

    To the best of my knowledge, we know the following.....

    Cop Vi: 0.0 m/s
    Cop Accel: 2.44 m/s2
    Spdr V: 30 m/s

    a) Formula: Vf = Vi + AT ????

    What should I use as the Cop's Final Velocity?
     
  2. jcsd
  3. Sep 13, 2006 #2

    J77

    User Avatar

    I presume you were given those answers...

    From the formula you give [tex]v=u+at[/tex], you need to integrate to get one for distance [tex]s=ut+at^2/2[/tex].

    You can then equate this formula using the data for both cars - it will be a quadratic with 2 solutions - one for the time when the cars are together at t=0 and the other for the time when they catch up.

    When you've got this time, the distance is easily found using the formula again.

    I haven't done this since school - it was a struggle remembering the method :biggrin:
     
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