1. Not finding help here? Sign up for a free 30min 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!

Differentiation car problem

  1. Dec 7, 2007 #1
    1. The problem statement, all variables and given/known data
    A car, travelling at a speed of 90km/h, approaches a stop sign 40m ahead. If the car immediately begins to decelerate at a rate of -8m/s^2, will it be able to stop in time? Justify your response


    2. Relevant equations
    d = 1/2at^2 + vt

    3. The attempt at a solution

    I found time by doing t = v/a and found it to be 25/8s
    Then I subbed it in d = 1/2at^2 + vt and got an answer of 39.1m, which is smaller than 40m. So it will be able to stop in time.
    But this assignment is all about differentiation, so I should be finding a derivative somewhere.... but I don't know where to find a derivative to solve this problem!!
    Please help~~
     
  2. jcsd
  3. Dec 7, 2007 #2
    Hello,

    Well, you've kind of already used differentiation, but you may not know it. You have an equation for position:

    [tex] x(t) = x_0 + v_0t + \frac{1}{2}at^2 [/tex]

    The velocity is found by taking the derivative of this equation:

    [tex] v(t) = \frac{dx}{dt} = v_0 + at [/tex]

    So when you calculated your time (where did you get t = v/a?) you were using this equation.

    Hope this helps.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Differentiation car problem
  1. A differential problem (Replies: 6)

  2. Differentiation Problem (Replies: 26)

Loading...