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Homework Help: A motorist avoiding hitting a deer

  1. Aug 25, 2008 #1
    1. The problem statement, all variables and given/known data
    Part 1:
    A motorist is traveling at 17 m/s when he sees a deer in the road 45 m ahead.
    If the maximum negative acceleration of vehicle is -7 m/s^2, what is the maximum reaction time (deltat) of the motorist that will allow him to avoid hitting the deer? Answer in units of s.

    Part 2:
    If his reaction time is 1.71654 s, how fast will he be traveling when he reaches the deer? Answer in units of m/s.

    3. The attempt at a solution
    I tried to use this equation: X(t)= X (initial)+ V*t + 0.5*a*t^2
    but it does not work and I stopped
    I can not think of a method to solve it

    Please help

  2. jcsd
  3. Aug 25, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Oh deer!

    hi hsbc2003! :smile:

    Hint: Start by working out how far he travels between starting to brake and coming to rest.

    Everything else should then become clear. :smile:
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