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Homework Help: Can't figure out this problem regarding two bodies with different accelerations

  1. Sep 5, 2005 #1
    I am so close to figuring this problem out, but I just can't quite get it. Here's the problem:

    At the instant the traffic light turns green, a car that has been waiting at an intersection starts ahead with a constant acceleration of 2.80 m/s^2. At the same instant a truck, traveling with a constant speed of 23.5 m/s, overtakes and passes the car.
    A) How far beyond its starting point does the car overtake the truck?
    B) How fast is the car traveling when it overtakes the truck?

    Here is what is given:
    car: Vyi = 0, Ax = 2.8 m/s^2
    truck: Vyi = 23.5 m/s, Vyf = 23.5 m/s, Ax = 0

    here is what i know:
    1)If graphed, y-axis being distance and x-acis being time, the truck would like like a straight diagonal line, while the car would be sloping up, crossing over the truck's path at some point (I'll call it X). I am trying to find X.
    2)I know I need to use two different kinematic equations and set them equal to each other, but this is where I start to not understand.
    3) So, what I am trying to find is when the distance of both equations are equal to each other? So solve a couple kinematic equations for D then set them to each other right? Here's what I get:

    (23.5 m/s)(T) = (1/2)(2.8 m/s^2)(T^2)

    which turns out to be T = 16.79 seconds..is this correct? If it is I can use it to get the final answers for both A and B. Thanks guys!!

    please don't waste your time with this, turns out I was right! :eek:
    Last edited: Sep 5, 2005
  2. jcsd
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