The Car Stopping Distance LogarithmicallyAuton pysähtymismatka logaritmisestiI 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 AsphaltSpeed 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) |