you need
  • - speedometer or radar;
  • - coefficient table;
  • - Calculator.
Braking is done by increasing the friction force, which is doing negative work, reduces the speed of the vehicle.Ideally, given that the work is going to change in the kinetic energy of the body, get the ratio in which the brake path S equals the square of the velocity v, k twice the gravitational acceleration g≈10 m / s² and the coefficient of friction of the road surface μ(S = v² / (2 ∙ μ ∙ g)).This does not include any vehicle weight, and the coefficient of friction varies with the weather conditions, the quality of the tires and the road surface type.The calculations need to take the speed of the car, which he had at the start of the braking
system.Measure it is possible by means of a speedometer or radar.
In real life, to determine the braking distance of a vehicle is used a formula derived practical way.In order to determine the braking path car, vehicle braking rate K, multiply by the square of its velocity at the beginning of braking v.Divide the resulting number by 254 and the coefficient f, which characterizes the degree of grip S = K ∙ v² / (254 ∙ f).For each of the factors has a range of values ​​that they can take.For example, a braking rate of the car is 1 and the truck takes the value of 1.2.The coefficient of grip can be set to 0.1 - for bare ice, 0.15 - for ice and snow, 0.2 - for snow-covered surfaces, wet roads for 0.4 and 0.8 for dry.
PrimerAvtomobil "Lada" started braking at a speed of 80 km / h, determine its path braking on dry asphalt road."Harmony" is a car, so the car coefficient is equal to 1. Since the road is dry, take the friction coefficient of 0.8.Substitute a value in the formula and get the S = 1 ∙ 80² / (254 ∙ 0,8) ≈31,5 m.
This formula does not account for the extent of wear of tires and brake pads car, and actual results maybe somewhat different.But in any case, the error is not more than a few meters.