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Homework Help: Need help with simple acceleration problems.

  1. Oct 7, 2007 #1
    Here's one:

    Craig got up to 133.5 km/h getting around a slower vehicle within the length of the passing lane. He then spotted a police cruiser coming around the corner and hit the brakes, slowing to 100 km/h in 0.9 seconds. How much distance did he travel in this time


    So I'm pretty much confused with accleration problems and identifying intial velocity and final velocity. I kow that t=.9 secs. So is the initial velocity 133.5 km/h and final velocity is 100 km/h?

    Would I first use the delta s=vi(t)+ 1/2(a)t^2 equation to find the displacement of when he slowed down?
     
  2. jcsd
  3. Oct 7, 2007 #2

    mjsd

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    Homework Helper

    yes.

    to use this you need to assume that acceleration is constant. at this stage you have only 3 known variables: u, v and t. but from these you can work out the average (de)acceleration
     
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