A car is a vehicle that has wheels, carries a small number of passengers, and is moved by an engine or a motor. Cars are also called automobiles or motor vehicles. Trucks and buses are motor vehicles as well. However, trucks and buses are larger than cars, and they carry heavier loads.

It is hard for anyone today to imagine what life was like before there were cars. Cars and other motor vehicles have made it easy for people to travel within a city or across a continent. They have also influenced where people live. People once had to live near their jobs, but now they can live farther away and drive to work.

Yet cars and other motor vehicles have brought problems as well. Tens of thousands of people are killed or injured each year in traffic accidents. Cities are often congested with huge traffic jams. And gasoline is a limited resource that pollutes the atmosphere when burned as fuel.

                 Car bodies have come in many different types. In early days most cars were open, without a fixed top. Now, aside from convertibles, most cars are closed. The most common styles include coupes andsedans. A coupe is a two-door car with a small back seat. A sedan usually has four doors and seats four to six people. Sedans with a lift-up rear door are called hatchbacks. Sports cars are built low to the ground and usually have no back seat. Station wagons have extra carrying capacity. By the end of the 20th century, however, they had been mostly replaced by minivans and sport utility vehicles (SUVs). Some cars are specially designed and built to be used for racing.

Parts of a Car

Many parts work together to make an automobile run. 
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All cars have certain basic parts. The body of an automobile is the outer shell that encloses the vehicle's mechanical parts and its passengers. Most auto bodies are made of steel, but some are made of strong plastics or fiberglass. The body is attached to thechassis. This consists of a frame that holds all the other major parts of the car together. Those other parts include the engine, a steering system, brakes, and the wheels.

How Cars Work

A driver operates a car by pressing on pedals to make it go and stop and by turning the steering wheel to guide where the car goes. The pedals and steering wheel work because they are part of a larger system.

Engine and Related Parts

In an internal-combustion engine a spark plug ignites fuel that is released into a cylinder. The … 
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Most cars are powered by internal-combustion engines. In such an engine a mixture of air and gasoline enters a tubelike cylinder through valves. There the mixture makes small explosions. Each explosion produces gases that expand rapidly and push against a device called a piston on one end of the cylinder. The piston goes up and down as the gases expand and contract. Rods connected to the pistons convert that movement into the power that eventually turns the wheels. Most car engines have four to eight cylinders.

The air-fuel mixture that enters the engine cannot ignite by itself. It needs an electric spark. This comes from devices called spark plugs. They get their electric current from a battery. The car's lights, horn, turn signals, windshield wipers, starter, and instruments such as the gasoline gauge are also powered by the battery.

An exhaust system carries burned gases from the engine to the muffler. The muffler cools the gases. It also reduces their pressure. This reduces the noise coming from the tailpipe. Modern cars are also equipped with a device called a catalytic converter. The catalytic converter uses chemicals to reduce exhaust pollution.

An internal combustion engine gets very hot. Cars therefore must have a cooling system. In a liquid cooling system, coolant (water and antifreeze) flows through passages around the cylinders and carries off this heat. The hot coolant is then pumped through a radiator to cool it off. Some engines are cooled by a flow of air and have no liquid coolant.

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