# Most effective way to stop a car on a slippery road

#### denian

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:
Related Other Physics Topics News on Phys.org

#### LURCH

Re: friction

Originally posted by denian
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.
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.

#### denian

tq lurch
hope for more respond.

#### arcnets

Re: friction

Originally posted by denian
(b) sufficiently, so that skidding does not occur.
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.

#### russ_watters

Mentor
Re: Re: friction

Originally posted by arcnets
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.
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.

tq so much guys.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving