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Homework Help: Please, can someone help me with this reaction problem!

  1. Nov 11, 2008 #1
    1. The problem statement, all variables and given/known data

    A ranger in a national park is driving at 47 kilometers per hour when a deer jumps onto the road 72 meters ahead the vehicle. After a reaction time of t (s), the ranger applies the brakes to produce an acceleration of -2.6 meters per second squared.

    What is the maximum reaction time allowed if the ranger is to aviod hitting the deer? Answer in units of (s)

    Vi = 47 km/h

    d or delta x = 72

    a = -2.6 m/s^2

    delta t = ?
  2. jcsd
  3. Nov 11, 2008 #2
    keep in mind that during the reaction period delta t, the velocity of the ranger is 47 km/h

    after the delta t is passed, the velocity is reduced to 0 because of the negative acceleration -2.6

    You really need to split up the question in 2 parts :

    1) during the delta t
    2) once the delta t is finished and the ranger is actually applying the break.
    So, what formula's do you know to calculate velocity and position as a function of time ?

    Also, pay attention to the given UNITS !!!

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