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Kinematics Problems

  1. Jul 12, 2010 #1
    1. The problem statement, all variables and given/known data
    1) A driver is traveling at 25m/s when she spots a sign that reads "Bridge Out Ahead". It takes her 1.0 s to react and begin breaking. The car slows down at a rate of 3.0 m/s2. Luckily, she stops 5.0m short of the washed-out bridge.
    (a) How much time was required to stop the car when she spotted the sign?
    (b) How far was the driver from the bridge when she first noticed the sign(keep in mind her reaction time)

    2. Relevant equations

    3. The attempt at a solution
    25 m/s / 3m/s2 = 8.3seconds + 1 second (reaction time) = 9.3 seconds.
    b)
     
  2. jcsd
  3. Jul 12, 2010 #2
    For (b) there is one of the four kinematics that is particularly useful for this problem and many others being that you are given an initial velocity, an acceleration, a final distance, and you just found the time coordinate from completing (a). Which of the kinematics incorporates these all of these variables as well as pertaining to a displacement? That ought to get you in the right direction.

    Joe
     
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