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Homework Help: Motion with constant acceleration

  1. Feb 22, 2009 #1
    I'm having trouble finding the equation.

    Two cars are traveling along a straight road. Car A maintains a constant speed of 80 km/h and car B maintains a constant speed of 110 km/h. At t=0, car B is 45 km behind car A. (A) How much father will car A travel before car B overtakes it? (B) How much ahead of A will B be 30 seconds after it overtakes A?
  2. jcsd
  3. Feb 22, 2009 #2


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    It's all constant speed,

    All you have to know is that V*t = d
  4. Feb 22, 2009 #3
    I'm still not sure how to figure it out.
  5. Feb 22, 2009 #4


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    Look at the differences in speed.

    How long to make up the difference in distance?
  6. Feb 22, 2009 #5
    Try writing the distance from the position that car B is at t=0 as a function of time (In other words, place your origin at that point. It may help to draw a simple diagram).
    For example, dB(t) = vBt = 110t (m). Try finding dA(t). Since you are measuring both distances from the same origin, you want to find the time t that the functions are equivalent.

    Note that this is a very rote approach. Try LowlyPion's intuitive way first.
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