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Homework Help: Help understanding how an equation is manipulated

  1. Oct 12, 2009 #1

    You are stuck behind a slow driver, there is a 1 km passing lane between a slow car and a truck. In order to properly pass you must be at least 40m from the slow car. You are travelling at 70km/h and there is an oncoming truck travelling at 80km/h. Each car is 4m long. What is the minimum acceleration you would need.

    Figuring out the final answer isn't the problem, just the manipulation of the next equation to find maximum time it would take. I don't get how this works out, could somebody should me step by step on how to turn d = vt into:

    d = v(car)t + d + v(truck)t

    Entering numerical values makes it:

    1000m = v(you)t + 44 + v(truck)t

    D = vt is the equation that was used, I just don't understand how they got put together in this way.

    d = vt
    1000m = 19.44m/s(t)
    1000m/19.44m/s = 51.44

    1000m = 22.22m/s(t)
    1000m = 22.22m/s(51.44)

    That doesn't equal 1000m.
  2. jcsd
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