Math CentralQuandaries & Queries


Mr.Adjetey, a student:

you are travelling at 30km/h. According to the rule of thumb,the braking distance is 9 metres when braking normally.How long is the braking distance under the same conditions when travelling at 60km/h?

Hi Mr. Adjetey,

The long way to do this question is to solve for μ, the friction coefficient of the road, using 30 km/h information then solving for 60 km/h. The short way is to consider the formula for distance and think "If I double velocity, how will it effect distance?"

Hope this helps,



About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS