machines

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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 un-

der the large stones to

make mobility easier.

Ramps (inclined planes)

were built to raise the

stones onto the pyramid

structure.


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.

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

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

SIMPLE MACHINES

Other machines, like com-puters, are very recent inven-

Pulley

Rope

Lever

Wheel and axle 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.

axle cart


The pulley

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

A double pulley

The inclined plane or ramp

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

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 in-clined 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


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 ful-

crum and the load.

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.


COMPOUND MACHINES

Compound machines are made up of many parts, some of which are simple ma-chines. Bicycles, cars or computers are examples of compound machines.

GEARS

Gears are one of the basic com-pound machines. They are made of pairs of gear wheels that have teeth along the outside edge.

The teeth of two gear wheels fit to-gether. When one gear wheel turns, it will make the other turn too.

Gears are used in windmills, mechanical watches and bicycles.

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.

grindstone

axle

gear

gear

Windmills work with

gears. Two gears at a

right angle transmit the

force to a grindstone

that grinds wind.


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 inter-connected computers. We can send e-mail messages and search for a wide range of information.

Computers process texts, images and numbers. They enables you to use the internet

and communicate with e-mail.

Screen

Modem

System unit

Mouse

Speaker

Printer

Keyboard

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