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# Why there are accidents? Coefficient of coupling of

of Accident on roads always happen suddenly. Just you rushed, enjoying confidence in the forces, and suddenly, without any visible reasons, appear in a ditch or face other car. Also you count losses …

But whether so this accident is sudden? Whether only you are guilty of it? And whether you have to pay expensive repair?

So if you drive, you have to understand some concepts.

- it the unpleasant phrase directs coupling coefficient at memories of outstanding homeworks. But it is necessary for you if not to fall in love with it then to have the same clear ideas of it as, for example, about “frontal loading“. And at you it will turn out - right now.

We will assume, your car weighs 1000 kg. It is affected by the gravity pressing it to the road. The scientist Newton established that it is equal to the mass of the car increased by the acceleration of gravity which on a surface of our planet makes about 10 meters per second for a second of falling. Thus, the gravity operating on your car will make 10000 kg * m/s 2 , or 10000 Newtons (further “N“).

Two women, even on heels, will be able easily to push or pull such car, applying force about 500 N

But we will try to make so that wheels did not turn, having strongly pressed on a brake pedal. Then the car cannot almost be shifted. On dry asphalt efforts of two tens women will be required dragging to drag the car. Having put their efforts, we will find out that the car will move a little if to apply force about 7000 N. On the dirty road it will be much easier to shift the car - only 3000 N are necessary and if the car stands on ice, there will be enough 1000 N

the Relation of two forces at all - forces necessary for shift of the car with the blocked wheels, and the gravity pressing the car to the road are called in coupling coefficient .

So we can easily receive coupling coefficients for dry asphalt - 7000/10000 = 0,7, for the dirty road - 3000/10000 = 0,3, and for ice - 1000/10000 = 0,1.

These values approximately same and in case to pull the car sideways. Why to you it is the nobility?! The insufficient attention to coefficient of coupling or its wrong assessment is the main reason for accidents on roads, especially in the spring and in the fall when from - for it there are about 70% of accidents.

Without coupling with the road the car will not be able tronutsyas places, to slow down or turn. Huge efforts of scientists, road builders, producers of tires are directed to increase of coefficient of coupling and its preservation for a long time under any weather conditions. It is surprising that such efforts pass out of attention of many motorists.

So, motors of modern cars develop the huge force with which driving wheels make a start from the road - a torque . If the torque is more, than force of adhesion with the road, wheels are scrolled and the car cannot start. The some of coupling, the stronger you can press on the accelerator pedal, the quicker the car gathers speed.

To the contrary, the some of coupling, rather a car will stop if to resort to emergency brake application.

We will try to define when your car moving with a speed of 60 km/h on wet asphalt which coefficient of coupling 0,4 stops if strongly to press a brake pedal. What way it at the same time will pass?

At first we will express car speed in meters per second:

60 x 1000: 3600 = 17 m/s

Time to a full stop are equal to the speed of the car divided into coefficient of coupling and on acceleration of gravity:

Stop time = 17 m/s: 0,4: 10 m/s 2 = Distance which at the same time will overcome the car are equal 4 seconds

to work of average speed of the car for a while to a full stop:

Distance = 17 m/s: 2 x 4 with = 34 meters

At increase in speed twice, to 120 km/h, the brake way will increase by 4 times - to 136 meters!

Do not forget to add time of reaction of the driver to the received results.

Often the question of attraction you to material, administrative or, God forbid, to criminal liability is directly connected with the correct assessment of coefficient of coupling.

So, the minimum coefficient of coupling on roads for the tire having protector drawing makes 0,4, and on dangerous sites - turns, intersections, before crosswalks and stops - 0,45. It is watched by road builders.

If you became the participant of road accident, being driving the car, try to record a condition of a road surfacing, make it a photo throughout a brake way. When in a week or month the expert estimates coefficient of coupling of the road on the place of road accident, its assessment will sound approximately so: 0,4-0,6 depending on weather conditions, a condition of a protector of your tires and pressure in them. In your interests that the court considered that, for example, pressure in tires met standard, but asphalt was worn-out, there were bitumen sweatings, there was a rain and the coefficient of coupling made only 0,3-0,4, and, thus, you could not avoid collision owing to force majeure. So, you could not be made responsible.

Except coupling coefficient, there is one more important factor about which it is necessary to know - turn radius...