Instruction

1

To calculate

**the speed**of the car at its braking**path**, recall first some concepts. The distance passed by vehicle (car, tram, train, etc.) since the discovery of the danger the driver to stop, called the stopping distance. It includes the distance that the car was for the time spent on the reaction of the driver, the distance traveled-so far so good brake system or braking distance. Time spent on driver reaction is the time from the moment the driver detected the danger of committing the necessary actions, for example, pressing on the brake pedal. This time can be from 0.2 to 1, 2 seconds. All depends on the skill of the driver, his state of health, weather conditions. The time spent on the stopping distance depends on the condition of the brake system, usually believe that it is equal to 0,2 seconds.2

Braking distance is the distance that the vehicle has passed from the moment of pressing on the brake pedal to a complete stop. It depends on speed, road surface, weather conditions, condition of the brake system and wheels, method of braking, the weight of the vehicle.

3

To calculate the initial

Va - initial

t3 - rise time of deceleration of the car in seconds;

j - steady-state deceleration of the vehicle during braking, m/S2; note that the wet coating-5m/S2 according to GOST 25478-91, and to dry coating j=6,8 m/S2, hence the initial

U - length brake track (SW), measured also in meters.

**speed**of the vehicle (VA), given the length of braking trace, you can use the formula.Va = 0.5 x t3 x j + √2Ѕю x j = 0,5 0,3 5 + √2 x 21 x 5 = 0,75 +14,49 = 15,24 m/s = 54.9 km/h where: in the expression √2Ѕю x j,Va - initial

**speed**of a vehicle, measured in meters per second;t3 - rise time of deceleration of the car in seconds;

j - steady-state deceleration of the vehicle during braking, m/S2; note that the wet coating-5m/S2 according to GOST 25478-91, and to dry coating j=6,8 m/S2, hence the initial

**speed**of the car when the "SW" in the 21 meter is equal 17,92 m/s, or 64.5 km/h.U - length brake track (SW), measured also in meters.

# Advice 2 : How to determine stopping distance

Any motorist should be able to determine the braking

**path**. From this often depends the safety of the driver and those in the car besides him. What is the braking**path**and how to define it, to avoid trouble on the road?You will need

- car, road

Instruction

1

The brake

**path**is the distance that the car passes after the brake system and to a final stop. The braking distance depends on many factors: the speed of the vehicle, method of braking and the conditions, that sets expensive. The greater the speed, the greater the braking**path**.2

In addition to the aforementioned factors, the most important road surface and its condition, weather, weight of vehicle, as well as the technical characteristics and the condition of the wheels and braking system. The minimum stopping distance is on a dry paved road, the largest is on the ice. Accordingly, along with the increase of braking distance is increasing the danger.

3

Of course, in an emergency, to calculate a braking

**path**is extremely difficult, but you should imagine the possibilities for your car in this plan to making the right decision at the right time. There is a formula that can determine the braking**path**. Motorists are advised to use it before getting behind the wheel, as this can prevent many unwanted incidents.4

The formula is: S = Ke x V x V/(254 x FS). It is necessary to explain the legend. S is stopping distance in meters, Ke is the coefficient of inhibition, which for passenger cars is always equal to unity, V is the initial speed when braking, measured in km/h, and FS is the coefficient of traction, depending on its state (dry pavement – 0,7, wet the road is 0.4, in the case of compact snow is 0.2, and 0.1, if the road is covered with ice). Determination of braking distance is a simple and useful effect, available to each motorist. It is sufficient to substitute in the formula the numbers appropriate to the specific situation and settings of your machine.

# Advice 3 : How to determine the speed of the car

Vehicle speed is constantly changing during the trip. Determine what speed the car had at one time or another way, very often involved in both the motorists and the competent authorities. Especially because ways to learn the speed of the car a huge amount.

Instruction

1

The easiest way to determine the speed of the car is familiar to all from school. To do this you need to fix the quantity of kilometers you drove and the time in which you overcame the distance. The speed of the car is calculated according to the formula: distance (km) divided by time (h). So you will get the desired number.

2

The second variant is used when the vehicle stopped abruptly, but the basic measurements like time and distance, nobody spent. In this case, the vehicle speed is calculated by its stopping distance. For such a calculation even has its own formula. But it can be used only if the left braking marks on the road.

3

So, the formula is as follows: the initial velocity of the car is equal to 0.5 x the rise time deceleration (m/s) x, the steady-state deceleration of the car when braking (m/S2) + root of the length of the braking path (m) x, the steady-state rate of vehicle deceleration during braking (m/S2). The value called "steady-state deceleration of the car when braking" is fixed and only depends on what the asphalt was the place to be. In case of dry road in the formula, substitute the number of the 6.8 it is written in a FR used for calculations. For wet asphalt this value will be equal to 5.

4

To determine the speed on braking distance, and another according to the same formula. It looks like this: S = Ke x V x V / (254 x FS). To substitute in this formula have the following values: braking coefficient (Ke) for passenger cars during this value is usually taken 1, speed at beginning of braking (V), coefficient of traction (FS) for different weather conditions identified its value: dry pavement - 0,7, wet road - 0,4, Packed snow - 0,2, icy track is 0.1.

5

You can determine the speed of the car in a certain gear. For this you need following values: the number of revolutions of the crankshaft (Nc), dynamic wheel radius (R), the gear ratio (in), gear ratio of a pair (irn), the initial vehicle speed (Va). Calculate the speed according to the formula: Va = Nc x 60 x 2pi x R / (1000 x in x irn).