Automobiles are one of the most common ways people get around today. They are faster than walking and far more convenient than riding a bicycle, bus or train. They burn a lot of fuel and cause pollution, but many people find that the advantages of having their own automobile outweigh the negatives. They can also take you to places that are inaccessible by public transportation, and they allow you to have a certain degree of privacy, since you don’t have to rely on other people for transportation.
The word “automobile” is from the Greek words for self and move, meaning that cars move on their own without needing horses or any other external power to make them go. Automobiles are designed to run mainly on roads, seat one to eight people, have four wheels and primarily transport passengers, rather than cargo. The branches of engineering that deal with the manufacture and technology of these vehicles are known as automotive engineering.
There are many types of automobiles, depending on the needs and preferences of individual drivers. Some are designed for off-road driving, while others are built for high-speed road use. Most are powered by internal combustion engines, but electric cars also exist.
Throughout the centuries, inventors have worked to create a car that would be practical and affordable for the average person to own and operate. They have experimented with steam, gasoline, and electricity as the source of power. By the end of the 19th century, gas-powered cars had replaced steam and electric vehicles as the primary means of transportation in the United States and Europe.
In the early 1800s, automobiles were often pulled behind wagons. Later, some people created a more advanced type of automobile that used a steam engine to drive wheels. These vehicles had a very limited range, however, because the steam engines were heavy and required a long time to warm up. Other inventors tried to develop automobiles that ran on batteries or electrical power, but none of these vehicles became popular enough to replace the horse-drawn wagon.
Many modern automobiles have brakes that use friction to slow the vehicle down or stop it from rolling when parked. Other brakes, called regenerative brakes, convert some of the energy that was used to propel the automobile back into electricity, which can then be reused to accelerate it forward again.
Some governments regulate the emissions from automobiles. They test vehicles on a dynamometer, which simulates driving conditions, to ensure that the car meets air quality standards. Other regulations test for durability and safety. For example, the 50,000 mile durability cycle tests a car’s ability to withstand repeated acceleration and hard braking over a course of 50 miles. Other testing requirements include crash test results and the presence of antilock braking systems.