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Homework Help: Question regarding motion of vehicles

  1. Sep 24, 2009 #1
    1. Question:

    You are driving your car (take the direction to be positive) at 20m/s. A van is following you, also at 20m/s. When you see a fog bank ahead of you, you hit the brakes (take this to be the time t=0). The driver of the van sees your brake lights and applies her brakes 1 second later. Both you and the van, when braking, have a constant acceleration of 5m/s^2 magnitude until coming to a stop.

    After the van and the car have both stopped, are they further apart, closer together, or the same distance apart than at t=0? How much, in meters, has the distance between them changed?

    How far behind the car should the van be at t=0 to avoid a collision?

    2. Relevant equations:

    Area under the graph of velocity versus time = distance travelled

    3. The attempt at a solution

    The van and the car are further apart after stopping.
    Distance travelled by car after t=0:
    Distance travelled by van after t=0:
    Change in distance=60m-40m=20m

    The car and the van have to be at least 20m apart to avoid collision.

    p/s: Is this correct? Thank you very much! =)
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
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