1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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

    2. Relevant equations

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

    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


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    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


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member
    2017 Award

    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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted