Machines and How They Work [antikvár]

WHAT IS A MACHINE? A machine is a device that has been built to do a job. Machines have a number of different parts, and these are arranged to work together to do something usefiil. The earliest machines had only a few parts (pages 8-9). Many of today's machines are much more complicated. This book is mainly about mechanical machines -ones that convert one sort of movement into another. When you ride a bicycle, for example, your feet go round and round but the bicycle moves forward in a An age of machines In a day, you might use dozens of different machines, for cooking food, telling the time, entertaining yourself, or for getting about. Many specialized machines are also used in factories, in the air, or in the sea. Some produce things we need, and some make other machines. Without machines, our lives would be unimaginably different! Trains These were the first machines to make fast, long-distance teavel possible. Today, they reach speeds of up to 236raph (380kni/h). More about trains on pages 20-23. Straight line. A windmill works the other way around. It converts the movement of the wind - in a straight line - into the movement of grindstones, which ttirn round and round. Simple machines, like the bicycle, are powered by muscles. Many of the machines in this book are powered not by muscles but by fuel. Fuels such as coal, oil and gasoline contain energy that is locked up. Energy is released when the fiiels are burned. It produces more power for movement, making it possible to perform certain tasks faster. Bicycles Like trains and cars, bicycles use wheels and bearings to reduce friction. Together, these help to