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!

Car breaking speed physics priblem

  1. Sep 8, 2007 #1
    Problem: a typical automobile under hard braking loses speed at a rate of about 7m/s^2. the typical reaction time to engage the breaks is about 0.50 seconds. a school board sets the speed limit in a school zone to meet the condition that all cars should be allowed to stop in a distance of 4 meters
    a)what maximum speed should be allowed for a typical automobile
    b)what fraction of the 4 meters is due to the reaction time

    any ideas?
  2. jcsd
  3. Sep 8, 2007 #2


    User Avatar

    Staff: Mentor

    Well one needs to look at the distance D traveled in the reaction time of 0.5 s, and in that time use distance = speed * time.

    Then if something is traveling at speed V and is decelerating to a stop, then V2 = 2ax, where x is the distance traveled for an initial velocity V with a deceleration of a.

    So D is the distance traveled during the reaction time period and the total distance traveled is 4 m.

    See - http://hyperphysics.phy-astr.gsu.edu/hbase/mot.html


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

Have something to add?

Similar Discussions: Car breaking speed physics priblem
  1. Speeding cars (Replies: 1)

  2. The speed of the car (Replies: 1)