Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Most effective way to stop a car on a slippery road

  1. Aug 2, 2003 #1
    i get this question from a physics book

    the most effective way to stop a car on a slippery road is to press and release the brakes repeatedly. discuss whether this method will stop the car in a shorter distance as compared to when the brakes are applied :-
    (a) very hard, so that the wheels stop rotating
    (b) sufficiently, so that skidding does not occur.

    i cant find the answer for this q. hopefully someone can help me out. tq.
    Last edited by a moderator: Feb 5, 2013
  2. jcsd
  3. Aug 2, 2003 #2


    User Avatar
    Science Advisor

    Re: friction

    Obviously, (a) will cause the car to lose traction and slide for a greater distance.

    (b) should stop the car in the shortest distance, since it allows for the maximum, or forced to be transferred between the tires in the pavement.

    Pumping the brakes is a way to determine the model forced it can be applied before breaking the traction of the tires, but at the cost of releasing pressure and allowing the car to roll freely for short periods of time throughout the breaking process.
  4. Aug 2, 2003 #3
    tq lurch
    hope for more respond.
  5. Aug 2, 2003 #4
    Re: friction

    denian -
    in Germany, some cars have a computer-contolled device called ABS (Antiblockiersystem) which does exactly that. ABS are quite expensive, but worth the cost since they allow you to keep maximum control over your car.
  6. Aug 2, 2003 #5


    User Avatar

    Staff: Mentor

    Re: Re: friction

    They of course have ABS in the US too. But you are wrong about what anti-lock brakes do. They apply increasing pressure unitil the car starts skidding, then release and repeat. Its what denian was describing in the pumping and releasing the brakes. Thats why when you press hard on the brakes you feel it shuddering.

    ABS does not have a constant braking force and as such INCREASES your stopping distance when compared with using a constant force.

    denian - Lurch's explanation was exactly correct.
  7. Aug 2, 2003 #6
    tq so much guys.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook