The increase in speed makes the laws of physics become more and more important to the driver. These laws, even if they are not enforced by a police officer or written by a law making body, are absolutely binding on all drivers and no one can relax their effect. The laws of physics control each and every object that moves. The particular laws that apply to driving cover areas such as friction, centrifugal force and inertia, impact, and gravity. You should always remember that these laws apply to both city driving and highway driving, because their importance increases proportionally with the speed at which you travel. However, this article on highway driving would seem like the best place to discuss its importance.
Proper vision requires sufficient light and time for an image to be imposed on the retina of the eye, transmitted to the brain, and thus trigger a reaction from the driver. This means that road signs, signals, and pavement markings become increasingly important when driving at higher speeds. These give the driver advance warning of any curves, hills, intersections or railroad crossings that may lie ahead, as well as anticipated maneuvers by other drivers. A driver must learn to recognize all signs and signals instantly, since at higher speeds the recognition and reaction time becomes shorter and shorter. For ease of recognition, signs and signals in the United States are standardized by shape and color and can reflect light to be seen at night. Remember, it takes time to observe a sign, signal, or condition and then react to it. The reaction time of a given driver is fairly constant, but the distance traveled in this time is directly related to speed. Therefore, stopping distances and distances required for evasive action increase as speed increases.
Friction
Friction is the force that opposes the movement of one surface over another, and is the means by which a vehicle can move in a straight line, or can turn or stop. This force is exerted entirely through four small areas of friction, also known as tires. If we assume that the average reaction time is 0.75 seconds, common sense tells us that the faster the car travels, the longer the distance it will take to stop. The difference in stopping distance from 40 miles per hour to 70 miles per hour is about 3.5 times that. This means that if you can stop within 100 feet at 40 miles per hour, you’ll need 350 feet of headroom to stop traveling at 70 miles per hour.
However, these conditions only occur part of the time: if the frictional force is reduced by ice, snow, rain, oil, mud, loose gravel, a rough surface, or poor tires, stopping distances will drastically increase and evasive maneuvers will be reduced. become much more difficult, or even impossible. Since stopping distance increases faster than speed, it is important to allow more distance between your car and the car ahead as speed increases.
inertia and centrifugal force
If at any time the force of friction, or traction, between the four small areas of the tire and the road surface is lost, control is also lost, and one or both of the following physical forces can determine the situation: inertia, the tendency of a moving body to keep moving in a straight line unless an external force acts to change its direction of motion; and centrifugal force, the tendency of a moving body revolving around a center to fly away from that center. Centrifugal force can be demonstrated by placing a weight on the end of a rope and spinning it in a circular motion. If the rope comes loose or breaks, the weight will leave the circular path and continue in a straight line.
Obviously, a similar effect can happen to a turning vehicle. A car going around a curve must overcome centrifugal force in order to turn. If the centrifugal force is greater than the friction between the tires and the road, the car will not be able to turn, but will skid off the road. The key point is that friction increases with speed, but centrifugal force increases even faster. Therefore, the higher your speed, or the tighter the turn, the greater the chance that you will not be able to move safely. If you remember this principle, you will realize that you should slow down before entering a curve, especially if the road is slightly slippery.
The brakes should never be applied after entering a turn, as this tends to reduce friction between the wheels and the road. Remember, friction allows you to move your car, control it, and stop it. When you consider that for each tire the area that touches the road surface is approximately equal to the size of your hand, it’s understandable that many factors can cause loss of friction and consequent loss of control. The higher the speed, the greater the chance of this happening, and the greater the consequences. Speed should always be adjusted to suit road conditions.
In addition to the speed of the car, another factor that determines whether or not you will be able to turn safely is the angle at which the road banked into the curve. The easiest is a banked turn (similar to a race track); the second, a flat road surface; and the third, a crowned surface. The flat surface of the road is dangerous at high speed, and by comparison, in a curve, the cambered surface can only be negotiated at low speed because the car is leaning against the direction of the curve. When entering sharp curves, there is usually a speed warning sign that tells you the speed at which you can safely take the curve. The one who ignores these signs is indeed a very foolish driver.
Kinetic energy and impact force
If control of a car is lost, the usual result is a collision, either with another car or with a fixed object. The most important variable in this situation is the force of impact. The force of the impact itself is a function of the speed and weight of the car. If you double the speed of a car before a collision, the force of the impact is four times greater. If you triple the speed of the car before the collision, the force of the impact is multiplied nine times! Weight also plays a role here; if the weight of the vehicle doubles, the force of the impact also doubles. The total result of doubling the speed and weight of the vehicle would be eight times the force of impact. Therefore, any collision would necessarily be eight times more damaging. In effect, the impact of hitting a solid object at 30 miles per hour is like bringing down a three-story building.
Highway engineers use various techniques to reduce the force of impact in cases of unavoidable contact with surrounding objects. Smooth metal guardrails allow a car to bounce instead of hitting it solidly. Wide shoulders of the road, free of obstacles such as trees, culverts, and bridge abutments, help reduce the hazard. When lighting and signage standards are essential, these poles are designed to be easily cut or broken on contact. The best way to ensure that the force of impact does not act on your car is to always drive in a way that avoids collision with any and all objects!
The force of gravity
Gravity, the force that pulls objects toward the center of the earth, will cause cars to slow down going up hills, reducing their stopping distances; and to accelerate down hills, thus increasing your stopping distances.
A good driver will slow down going down a hill; On steep grades, you have to put your gear selector in low, so that the car’s engine acts as a brake. Hills are potential driving hazards for other reasons, too. They limit visibility; The driver should not pass or approach a hill, no matter how slowly the vehicles in front are moving, unless there is a passing lane. At the crest of a hill, the driver must watch for oncoming cars not in their own lane, or for obstacles in the road ahead, such as a car stopped while waiting to make a left turn. Remember that he must be able to stop your vehicle in the distance that he can see ahead, whether it is day or night.
