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Science & Technology

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Přidáno: 05.12.2010 11:19
Kategorie: Práce
Předmět: Angličtina
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Popis: Science & Technology


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Náhled materiálu: Pozor! Náhled nemusí odpovídat skutečnosti. (v náhledu chybí obrázky a formátování se může lišit)

Vít Pilnáček, 4.Y


Science & Technology

Today's society cannot imagine life without technology. Modern inventions are everywhere, even now in this very room. I wear watches that use microchip, I got electronic diary that uses microprocessor, most of us have cellular phone. Light in this class is provided by electricity.
Long time ago there was just a man and his load. Weight of his load was limited by his own power. Someone noticed, that there are some animals, they are stronger than a human and are also much faster. So it was decided to domesticate those animals (horses, elephants, donkeys, …) and let them carry special sleights.
Another first great man's invention was the wheel. It started new age of transport, because it was no longer needed to use sleighs. Wheeled carts could also transport heavier loads, because of their less friction. The wheel was one of many prerequisites for James Watt invention. Yes, I mean the steam engine.
Steam engine was firstly constructed in Britain and in started Industrial revolution that spread to most of Europe and to USA and Canada. The steam engine used the stretch of hot steam and transformed sliding move to rotating. It was very powerful and cheap to run (it used just water and wood or coal).
Steam engine was used in many other inventions such as railroad, heavy machines in industry, ships…). But it couldn't be used in planes, because the steam engine was too heavy for that. Problem of aviation was solved later, at a time when combustion engine was developed. This engine uses stretch of gasses that are produced by fuel's explosions. It's more effective, more powerful, less heavy, smaller but also more expensive. No longer is needed to carry so much coal, because combustion engines use liquid or gas fuel. Combustion engine started new generation of vehicles used for personal transport. They are called automobiles (cars). Also planes have been equipped with c.engines and the quickly became the most powerful weapon in army.
Combustion engines can be divided into two main groups: Ignition (use petrol or LPG) and inflammable (also called Diesel - they use oil). LPG is new kind of fuel for ignition motors and it's very advantageous. Re-making the motor for this fuel is very expensive but after these changes are made the engine can use both of those fuels and using the LPG has half costs.
There are another four engine types. They're not used in cars, but are also very important:
Reactive - used in planes (it uses the Physical rule of Action and reaction; hot gasses are flowing very fast from the engine and that makes the engine move  


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