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Constant Acceleration of a motorist

  1. Dec 8, 2008 #1
    1. The problem statement, all variables and given/known data

    A speeding motorist traveling 120 km/h passes a stationary police officer. The officer <i>immediately</i> begins pursuit at a constant acceleration of 10.0 km/h/s. How much time will it take for the police officer to reach the speeder, assuming that the speeder maintains a constant speed? How fast will the police officer be traveling at this time?

    2. Relevant equations
    These are the equations we have to pull from in class:

    Vf=Vi + at
    D= Vit + 1/2at2
    D=1/2t (Vf+Vi)
    Vf2=Vi2 + 2aD

    3. The attempt at a solution
    I fixed the mixed units so that 120 km/h equals 33.33 m/s and 10 km/h/s equals 2.778 m/s2
    The officer's Vi is 0.
    Distance(D) of the motorist and Distance(D) of the officer should be the same, as well as their times(t).
    So, Dm=Do
    and tm=to
    I've tried solving the above equations for a distance or a time that i can then sub back in, but nothing seems to be working. I just need a little push in the right direction.
  2. jcsd
  3. Dec 8, 2008 #2


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    Homework Helper

    Write equations for motorist and officer starting at t=0 and apparently x=0 for each.

    When the X's equal then the motorist gets his ticket.
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