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: Kinematics Homework Help (2D motion)-Stopping over time

  1. Oct 13, 2013 #1
    1. The problem statement, all variables and given/known data

    You're driving down the highway late one night at 18m/s when a deer steps onto the road 41m in front of you. Your reaction time before stepping on the brakes is 0.5s and the maximum deceleration of your car is 12 m/s/s

    2. Relevant equations

    1) How much distance is between you and the deer when you come to a stop?
    2) What is the maximum speed you could have and still not hit the deer?

    3. The attempt at a solution

    Am I doing this right? She gives us the answer of 19m for the 1st question and 25m/s for the 2nd question. But I am coming up with a different answer for the first question.

    First I figured the distance between the car and deer to be 36m, after you take into account the 0.5s reaction time. Then I started to calculate distance it takes to stop.

    The equation I used was vf2 = vo2+2*a*d

    I plugged in the variables to get 0m2/s2 = 324m2/s2 + (-24m2/s2)*d ... I solve for d to get 13.5m, which is the distance traveled. Take 36m - 13.5m to get 22.5m from the deer, not 19m. I have not attempted the 2nd question yet because I thought I may be doing something incorrect.
  2. jcsd
  3. Oct 13, 2013 #2
    That should be 32.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted