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Homework Help: Need help with physics airplane runway question

  1. Oct 8, 2009 #1
    1. The problem statement, all variables and given/known data
    length of runway for airplane 1.5miles, accelerate at 3.0m/s^2 decelerate at 2.1m/s
    What length of time is available from the start of the motion to decide on a course of action (take off or abort)

    2. Relevant equations
    d=a*t 3.0m/s/-2.1m/s

    3. The attempt at a solution

    so far we have 804 seconds acceleration and -1149 seconds for deceleration
  2. jcsd
  3. Oct 8, 2009 #2
    The airplane is accelerating, or decelerating. This is the equation for constant speed.

    After 804 seconds of 3 m/s^2 acceleration, the speed of the airplane will be 1206 m/s.
    It will have covered 970 km

    suppose the airplane is accelerating until time T. How many meters does it move?
    If the airplane starts decelerating at time T, how long does it take before it stands still?
    How many meters does it move in that time?
    The sum of these 2 distances should be equal to the length of the runway, in the limiting case
    where the airplane is just able to stop in time. This will give you an equation that you can solve
    for T.
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