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!

Calculate the total stopping distance of the car

  1. Apr 9, 2016 #1
    1. The problem statement, all variables and given/known data
    reaction time of a driver to brake is 0,5s in that time the speed is constant
    the speed of a car is constant when he decides to slow down and to stop with -6,0 m/s2, the initial speed is 50 km/h
    Calculate the total stopping distance of the car

    2. Relevant equations
    Ve= -6,0*t +13,89
    t=2,3
    xe=-6,0*(2,3)^2 +13,89*2,3
    what did I do wrong?
    3. The attempt at a solution
    the solution has to be 23,03 m but I can't solve it,
     
  2. jcsd
  3. Apr 9, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    Hi eefje, Welcome to Physics Forums.

    FYI, you should list the standard equations that you will use in the relevant equations section, then show how you applied them in your attempt at a solution.

    I see that you didn't account for the distance traveled during the driver's reaction time period. How far does he travel before he bgins to decelerate?
     
  4. Apr 9, 2016 #3
    Hey Thank you for helping me, I will do it right the next time.
    In the 0,5 s he travels 6,945m i think (13,89*0,5). But I still can't solve it
     
  5. Apr 9, 2016 #4

    gneill

    User Avatar

    Staff: Mentor

    What basic equation are you applying for the period in which he decelerates?
     
  6. Apr 9, 2016 #5
    you mean in the 0,5s ? Δv= Δx/ Δt

    and after that: Δx= a*Δt^2+Δv*t
    Δv=a*Δt
     
  7. Apr 9, 2016 #6

    gneill

    User Avatar

    Staff: Mentor

    You're good for the first period (reaction time period). ##d = vt##

    For the second period where acceleration is happening you want the standard kinematic formula ##d = v_o t + \frac{1}{2} a t^2##.
    Note the "1/2" constant that multiplies the acceleration term.
     
  8. Apr 9, 2016 #7
    Thank you very much, I can solve it now. the 1/2 was a stupid mistake, but I didn't know that the distance in the 0,5 s important was. Thank you :)
     
  9. Apr 9, 2016 #8

    gneill

    User Avatar

    Staff: Mentor

    You're welcome. Good luck in your studies.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Calculate the total stopping distance of the car
Loading...