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Reaction time

  1. Oct 7, 2007 #1
    1. The problem statement, all variables and given/known data

    Determine the stopping distances for a car with an initial speed of 85 km/h and human reaction time of 1.0 s for the following accelerations.
    (a) a = -4.0 m/s2
    m
    (b) a = -8.0 m/s2
    m

    2. Relevant equations
    d=v1+v2/2 *t
    a=change in velocity/time


    3. The attempt at a solution
    I converted 85kh/h into 23.61m/s
    I found how many seconds in each instance
    (a) 5.9s...I did -4=(0-23.61)/t solved for t
    (b)2.95s...same as a
    using these times I used (23.61+0)/2 *Time then added 1 for the reaction delay

    I got (a)=82 and (b)=47

    What am I doing wrong?
     
    Last edited: Oct 7, 2007
  2. jcsd
  3. Oct 7, 2007 #2
    Subtract time.
     
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