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Homework Help: Motion with constant acceleration

  1. Sep 9, 2009 #1
    1. The problem statement, all variables and given/known data
    An automobile speeding at 28.33 m/s passes a stationary police cruiser. The police officer starts to move her cruiser in persuit 11.00s after the automobile passes. She accelerated uniformly to 34.72 m/s in 11s and then continues at uniform speed until she catches the speeder.

    How long does the police cruiser take to catch the speeder? How far from the initial position is the speeder caught?

    2. Relevant equations
    (I don't know!!!)

    3. The attempt at a solution
    I got that the speeder is 311.3 m ahead of the cruiser when the cruiser starts. I also got that the cruisers acceleration is 3.16m/s^2. I have also figured that when the cruiser gets to the uniform speed of 34.72 m/s, the speeder is 431.4 m ahead of the cruiser.

    I cannot figure out how to find out where and when they meet.
  2. jcsd
  3. Sep 10, 2009 #2


    User Avatar
    Gold Member

    So, you know the velocity of the cruiser, the velocity of the speeder, and the distance between them... You've got all the info, but no way to use it then.

    You are 2/3 of the way to the answer (finding cruiser acceleration and then distance between the two at t = 22s). I hate to give it away, especially since you're so close so I'll try to hint at it with a question.

    If you're driving a car and get into a head on collision with another car, what would be a simple way to describe the speed of the collision (say if you're going 30 and they're going 40)? Would it be best described as 30, 40, or some other number? That's relatively all I have to say. :wink:
  4. Sep 10, 2009 #3
    Thanks!!! I got it!
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