Car, Train - Physics

Braking Distance

Average velocity:

If the truck starts with twice the velocity, its average velocity will be twice as much as before, since:

average velocity = (starting velocity + ending velocity)/2

Time:

Newton's Second Law says:

acceleration of the truck = (net force on the truck) / (truck's mass)

Assuming that the brakes are applied with maximum force each time, the net force on the car due to its brakes will be the same each time. The mass of the truck will stay the same - therefore the acceleration of the truck will be the same in each case. Now:

acceleration = (change in velocity) / time

Since the change in velocity will be twice as much when the truck is initially going twice as fast, the time to stop the truck must double in order that the acceleration is the same.

Distance:

The distance the truck travels is given by:

distance = (average velocity)(time)

Since both the average velocity of the truck and the time to stop double, the distance to stop the truck will be four times as much (48 meters) when the truck's velocity doubles.

Stopping distance in relationship to speed

We must accept the fact that the faster we go, the further it will take us to stop. Several things must be considered to determine the stopping distance.


Your mental and physical condition is very important.

Of course, age, use of drugs, and physical fatigue will all affect your ability to react to a potential hazard, sometimes called perception and reaction time. Reaction time in daily driving can be as high as 1.5 seconds with various driving distractions.


The vehicle is another important factor to be considered in the stopping distance. Vehicles must have brakes that meet certain standards. We have even developed alternative braking systems such as Anti-locking Braking Systems (ABS).




The road and weather conditions all must be considered. As we discussed in another section of the manual, friction is the most important factor in stopping a vehicle.

When you are forced to stop, three things must happen. You must perceive the hazard or warning; react; and use your brakes to stop.

The length of time you take to identify, predict, and decide to slow for a hazard is called your perception time. You cannot consistently estimate your perception time because your ability to perceive will change from time to time. By scanning and maintaining the proper spacing method that we discussed earlier, you allow yourself more reaction time.


Once you know a hazard will be a problem, the length of time you take to execute your actions is your reaction time. An average driver's reaction time is ¾ of a second, in clinical laboratory settings. If you are impaired due to alcohol, drugs or fatigue, your reaction time will increase; thus the time to stop and distance that your car travels will also increase.

The distance your vehicle travels from the time you apply the brakes until your vehicle stops is called braking distance. These distances will change depending on your ability at the time, your vehicle conditions, and the conditions of the road. Estimating stopping distance can be hard so it is always better to utilize the two second rule. This rule enables you to project your approximate stopping distance under ideal conditions at any speed.

Don't forget, the higher the speed, the longer the braking distance. At higher speeds, you will have a harder time controlling your vehicle. A vehicle with worn tires or bad brakes needs a longer distance to stop. If the brakes on one side of your car are worn or out of adjustment, your vehicle will pull to one side in a stop. If you panic and slam on your brakes you might lose control of your car in an emergency situation. Remember wet road surfaces will reduce traction on the road and increase your braking distance.
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We have stopped teaching physics to our younger generation. We teach only Information Technology and our younger generation spend their entire day & night in Twitter & Facebook.

Wonderful roads.

High class road safety.

The best vehicle.

Our younger generation go abroad. They get the best of the best of vehicle and road. But they get involved in accidents.

Because, they have no idea about Newton's laws of motion;
Inertia;
Velocity;
v = u + at
F = ma

Our youth buys high-end car. But they have no idea about centrifugal force. They don't reduce the speed on the curve; get thrown away in the tangential motion.

Both Venkat and Sunil worked late night on the same project. Around mid-night, they get ready to leave. Just before entering the highway, Venkat crashed into Sunil's car.

Another incident. Our younger generation meet over the weekend for a birthday party. At the end of the party; no alcohol; they try to leave all at once. They bump into one another and exchange insurance information.

In this period; we convert humans into machines; may be thinking machines. They absolutely have no living skills.

Even a squirrel could save its life. These engineering college students went to Himachal Pradesh and died in the river. It is so sad; no basic living skill.

Many youth died in the simple swimming pool.

Our young generation do not learn Physics; no Chemistry; no Biology; only IT.

So, whether it is car; or train accident.

It's all about basic Physics.