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Name: ______________________________________ Class: ________________ Date: __________________

UNIT 7. MACHINES AND NEW TECHNOLOGIES BUILDING THE PYRAMIDS The ancient Egyptians built their gigantic pyramids on the west bank of the river Nile. Moving and cutting the heavy blocks was a hard job. They used simple machines to make this task easy:

 Workers used copper tools (wedges) to cut out the blocks in the quarries. Then they used wooden and bronze levers to move the stone blocks into position.

To transport the stone blocks, wheels wouldn't have been useful on the desert sand, so they placed wooden logs under the large stones to make mobility easier.

Ramps (inclined planes) were built to raise the stones onto the pyramid structure.

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MACHINES Machines make our life easier. Machines help us with different tasks. They transform energy to make the task easier. We save time and physical effort with machines.

Pulley

 Some machines are simple and humans have used them since ancient times, like the lever or the pulley.

Rope

Lever

 There are compound machines like watches or cars, which are made up of different simple machines.

Other machines, like computers, are very recent inven-

SIMPLE MACHINES Wheel and axle

axle cart

A wheel is a simple machine that rotates on an axle. The wheel was one of the most important inventions in human development. We can use them to transport people and things.

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The pulley

The inclined plane or ramp

A pulley is a wheel that is passed over by a rope. We use it to lift or lower objects in a controlled way and using less force.

The inclined plane is a surface that connects two different points at different levels. It makes easier to go up and down or to raise heavy objects from one surface to another with less effort.

.

A double pulley

A staircase is an inclined plane with steps

The wedge A wedge is similar to an inclined plane. This simple machine consists of a pair of inclined planes set face-to-face, that can sustain relative sliding or rolling motion. It does useful work by moving. In contrast, the inclined plane always remains stationary.

2 inclined planes

A wedge

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The lever A lever consists of a rigid bar that pivots on one point called a fulcrum. We push down forcefully on one end of the bar and the other end will move the object. We use a lever to move or lift objects. .

A lever is made up of three elements:

 The load (L) which is the object we want to move.

 The effort (E) which is the force we apply to the rigid bar.

 The fulcrum (F), which is the point which supports the bar.

Classes of levers Levers are divided into three classes, depending on the arrangement of their three components.

 First-class levers. The fulcrum is between the effort and the load.

 Second-class levers. The load is between the effort and the fulcrum.

 Third-class levers. The effort is between the fulcrum and the load.

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COMPOUND MACHINES Compound machines are made up of many parts, some of which are simple machines. Bicycles, cars or computers are examples of compound machines. gear

Windmills work with gears. Two gears at a right angle transmit the force to a grindstone that grinds wind.

GEARS axle

Gears are one of the basic compound machines. They are made of pairs of gear wheels that have teeth along the outside edge. The teeth of two gear wheels fit together. When one gear wheel turns, it will make the other turn too.

gear

Gears are used in windmills, mechanical watches and bicycles. grindstone

Sometimes gear wheels are not placed in contact with each other. Instead, a roller chain is used to connect the two wheels. The roller chain transmits movement. This system is found in bicycles and motorbikes.

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SCIENCE AND TECHNOLOGY IN THE 20TH C. During the 20th century, humans made great advances in science and technology. These are some examples:  In physics, atomic energy was discovered.

   

In chemistry, plastic and artificial fertilisers were discovered. Medicine advanced thanks to the discovery of antibiotics and other medicines, the use of high-tech devices and organ transplants. Mobile phones, radio, television, radar, artificial satellites and space travels allow us to communicate with the whole world and learn about outer space. Computer science has caused a true technological revolution in industry, research and communications. Today the internet is a worldwide network made up of millions of interconnected computers. We can send e-mail messages and search for a wide range of information.

Screen

System unit

Speaker

Modem

Mouse

Printer

Keyboard

Computers process texts, images and numbers. They enables you to use the internet and communicate with e-mail.

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machines  

machines information

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