Braking Distance in Physics
In physics, the friction is often calculated by the principle of understanding the braking event by car. In this context, without telling the friction-based calculation is not possible calculate for the stopping distance. Tyre tests are carried out through practical experiments for vehicles and tires are new. By default, the cars stop as long braking distance, but that is not even the case. Some cars are equipped with ABS brakes, Electronic Stability System, weight distribution differences etc. The braking test distances the average of the results and maybe ramaining the worst brakings. Which of these is your braking in a panic situation? In physics, the braking distance calculation does not take a position on reaction time and how it affects to different speeds. In addition, the friction-based calculations are made in an infinite rigid objects. Vehicles have the flexible suspension and tyre system. In practice, also the road surface at all is not the same at every point. The number of unknown variables is therefore high. Tyre tests are carried out in the winter environment on dry ice, summer tires on dry asphalt. The circumstances in which you have to brake, may significantly differ from professional drivers tests written. Tired after a long journey, sunshine etc. affect the braking distance .
The pure braking distance is directly proportional to the square of the speed (v2) and inversely proportional between the road surface and tire friction coefficient.
S = braking distance v = initial speed m/s μ = friction g = 9,82 m/s2
S = v2 / (2 x μ x g)
Friction
Static Kinetic
Wet asphalt 0.6 0,5
Dry asphalt 0,8 0.7
Wet ice 0,1 0,08
Dry ice 0,2 0,15
Dry road, driving speed of 100 km/h ( 27.78 m/s), wherein the dry asphalt friction coefficient of 0.8. Of this calculating, the stopping distance is 49 meters. The tests locking the brakes or without locking brakes on a flat concrete, the stopping distances were very nearly the same.
S = 27.782 /(2 x 0,8 x 9,82) m
S = 49 m
After this will be that which rarely are taken into account. For calculating minimum stopping distance, a value of 0.8 is a nominal value for the coefficient of static friction. The tabled values are for good tires and a good road surface. Almost always, coefficients of kinetic friction are less, and are dramatically less for wet, icy, slick, sandy, dirty very smooth or oily surfaces. With normally driven and worn tires, a smaller value such as .7 or .6. Poor condition tires might yield .5 or .4 for a closer representation of friction, this depending on the circumstances
Braking distance at 100 km/h speed is 49 m. How far is the braking distance at 50 km/h?
49/x = (100/50)2
(1002) x = (502) * 49
10 000 x = 122 500
x=122 500/10 000
x= 12.25 m
Check:
S = 13.882 /(2 x 0,8 x 9,82) m
S = 12,26 m
EP-calculation is not equations, but the previous example finds out the EP-calculation principle. Generally by knowing one value pair, the other value pairs are known. EP-calculation unlike the previous calculation is often on the area where the equations do not extend.
26.1.2021*14:30 (990 - 989)
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