The Car Stopping Distance Logarithmically
I dare say this approach is not presented elsewhere. The stopping distance is formed on reaction time and braking distance. A suitable reaction time is considered to be 1 second. This information is calculated in the table below. Values in the table are the average of the braking actions, so in traffic be prepared to the worst result.
S = Braking distance v = initial speed m/s μ = friction factor 0.8 g = 9.81 m/s2
S = v2 / (2 x μ x g)
Braking on the Clean and Dry Asphalt
Speed Reaction time Braking Tot.
km/h m m m
30 8.33 4.42 12.8 Known data 13 m
40 11.1 7.9 19.0 40/(Ln pii)6 = 17.8 m
50 13.9 12.3 26.2 50/(Ln pii)5 = 25.5 m
63 17.5 19.5 37.0 63/(Ln pii)4 = 37 m
80 22.2 31.4 53.6 80/(Ln pii)3 = 53.3 m
100 27.8 49.2 77.0 100/(Ln pii)2 = 76.3 m
120 33.3 70.6 103.9 120/(Ln pii) = 104.8 m
125 34.7 76.6 111.3 125/(Ln pii) = 109.2 m
An Example
As is known, the braking distance at 30 km/h is about 13 m. What has been roughly the speed of the car with a 71 m long braking mark?
30 / x = (13/71)2
(132) x = (712) * 30
169 x = 330750
x=330750/169
x= 130 km/h
Tarkistus - Check
S = 36.112 /(2 x 0.8 x 9.81) m (130 km/h = 36.11 m/s)
S = 83 m
Based on the table, the vehicle speed has been 120 to 130 km/h. On the motorway the vehicle has beeen within the limits. The more detailed information cannot determine of the braking marks.
3.2.2015*23:35 (1008 - 1002)
www.karikolehmainen.com
epcalculation@gmail.com |
