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Homework Help: Problem with distance in relation to acceleration.

  1. Aug 22, 2012 #1
    The problem statement, all variables and given/known data
    A 1200 kg car is at a red light on a horizontal road. When the road turns to green, (t0) he starts accelerating and reaches 14 m/s in 7 seconds. He then continues at a constant speed for 10 seconds, then brakes with a -3.5 m/s^2 acceleration.

    All accelerations are assumed to be constant.

    a) Calculate the amount of time he spends decelerating. (What I found through graphing : 4 seconds)

    b) Graph the speed in relation to time starting with t0. (Done successfully)

    c) Calculate the average speed in both the acceleration and deceleration phase. (7 m/s)<- this seems weird to me)

    d) Calculate the total distance between the start of the acceleration until the final stop.

    I'm having trouble with point d).

    The problem

    I don't understand how we can calculate a distance while the object is under acceleration. I can't wrap my head around it. Is there an equation I don't know about? Or am I overcomplicating things and it's just ( for this problem) an additional 2 meters per second during the acceleration phase, then 10 seconds of adding 14 m per second and then decreasing the number you add to your total by 3 every second starting by 14 during your deceleration? is it that obvious?

    Thanks in advance!
  2. jcsd
  3. Aug 22, 2012 #2

    Doc Al

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    Staff: Mentor

    Why not? It's moving isn't it? What's the average speed during each segment of the motion? Use that to find the distance traveled.
  4. Aug 22, 2012 #3
  5. Aug 22, 2012 #4


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