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Kinematic Equation Problem using Velocity & Distance

  1. Aug 31, 2014 #1
    Hey guys, I'm confused on this problem: It is a typical sunny day. Assume your reaction
    time is 0.50 s and the acceleration of your car is –8.2 m/s2. What is the no-skid stopping distance when the car’s speed is initially 26.9 m/s?

    1. The problem statement, all variables and given/known data
    a=-8.2 m/s^2
    v0=26.9 m/s
    v=0
    t=0.50s
    d=?


    2. Relevant equations

    d=v0(t) +1/2a(t^2)
    v^2=v0^2+2ad


    3. The attempt at a solution
    So I tried using the v^2=v0^2+2ad and got 44.12 m. However, the answer is 57.57. What did I do wrong? Thanks!
     
  2. jcsd
  3. Aug 31, 2014 #2

    SammyS

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    Hello dlang. Welcome to PF !

    Show detail regarding how you used the equations you gave.
    d = v0(t) +(1/2)a(t2)
    v2 = v02+2ad​
     
  4. Aug 31, 2014 #3

    Orodruin

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    What you have used is the formula for motion under constant acceleration which is true only after you have reacted. What about the distance traveled during your reaction time?
     
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