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Ahhh kinematics

  1. Apr 17, 2006 #1
    A police car stopped at a set of lights has a speeder pass it at 28 m/s. If the police car can accelerate at 3.6m/s/s (m/s^2),

    a)how long does it take to catch the speeder?

    b) How far would the police car have to go before it catches the speeder?

    c) what would its speed be when it caught up with the car?

    Sorry... for some reason I'm so confused at this... and I have no idea where to start... plus the answers are unreliable, so I have no idea if my attempts are on the right track or not. Please help:eek:
  2. jcsd
  3. Apr 17, 2006 #2


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    Welcome to PF Ash,

    You need to know at what time the cars have travelled the same distance, you are given their initial velocities and their acceleration, therefore, you need a kinematic equation with distance, inital velocities, acceleration and time. Can you think of one?


    Note to mods: please move this to Introductory Physics
  4. Apr 17, 2006 #3
    I have a bunch of equations from which to use, but I don't understand how to start part a. I've tried a million things, and nothing is close to the "right" answer....
  5. Apr 17, 2006 #4


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    There is only one kinematic equation which satisfies the conditions I posted above. Which is it?

  6. Apr 17, 2006 #5
    I dont' know... I don't know where to start?
  7. Apr 17, 2006 #6
    start by writing down what you have and what you need to know.

    then use your kinematics equations to solve for the variables you need to know.

    hope this helps. try posting what you have done so far, so that people can see where you need help.
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