7. Answer the following questions. There is just one correct answer to each of them.

1. Name three simple machines.

   1. Lever, crane, shovel; 

   2. Lever, wheel and axle, pulley;

   3. Lever, wheel and axle, computer;

   4. Wheel, axle, pulley.

2. Which best describes a block and tackle? It is a set of  

   1. levers;

   2. pulleys;  

   3. wheels and axles;

   4. cranes.

3. A door handle is an example of 

   1. a pulley;

   2. an inclined plane;

   3. a wheel and axle; 

   4. a lever.

4. Simple machines can be used to  

   1. both;

   2. increase force ;

   3. neither;

   4. increase distance.

5. The word fulcrum means  

   1. the axle in a wheel; 

   2. a lever;

   3. a pulley rope;

   4. the balance point of a lever.

6. A complex machine is  

   1. an electronic machine;  

   2. a combination of simple machines;

   3. an electric machine;

   4. the same as a simple machine.

7. A bicycle is a  

   1. simple machine;  

   2. complex machine;  

   3. Rube Goldberg machine;  

   4. none of the above.

8. A gear is a combination of which two simple machines?  

   1. Wheel and wedge;  

   2. Wedge and screw; 

   3. Lever and inclined plane;

   4. Wheel and pulley.

Unit 7 Part 1. Metals

1. Read and translate the following words and words-combinations:

armament, accidentally, alloy brass, Julius Caesar, the corrosive action of the atmosphere, copper, to hammer, to intend, to manufacture, non-metals, melting point, primitive man, wire, lead, zinc.

2. Read and translate the text. Memorize all highlighted words:

One basis of classification of the elements groups them into metals and non-metals. It is now 2,000 years since Julius Caesar was stabbed in a small auditorium known as Pompey's Curia and his body cremated in the Roman Forum. Since that time, many changes have taken place, but many things have remained the same. Steel is still the basic material of armaments, although, it is not used in the manufacture of shields and short swords. Gold, silver, and copper are, as 2,000 years ago, the coinage metals. Bronze is still used for objects in­tended to resist the corrosive action of the atmosphere, but now it has many competitors.

Knowledge of the metals, of course, has increased, greatly since Caesar's day. The Roman world knew, at least, copper, lead, gold, silver, tin, iron, mercury, and zinc (in a copper alloy). To this list, the twentieth-century's man in the street might add aluminum, magnesium, nickel, chromium, cobalt, tungsten, molybdenum, ura­nium, and one or two others. If he happened to be in­terested in aeronautics, he might add titanium.

The first metals which were used by primitive man were those that are found free in nature to a comparatively large extent. These are gold, silver, and copper. Tin entered the metal picture when someone discovered, probably accidentally, that if it was mixed with copper the resulting substance was harder. So there came into being the alloy that we call bronze, a material which was so important in the ancient world that its name is given to one of the cultural stages in human development. The Bronze Age began in Egypt around 3,000 before our era and in Europe some 500 or 1,000 years later.

Since almost no iron exists free in nature, it undoubtedly came into general use somewhat later than those just mentioned. However, the Egyptians and Assyrians made some use of iron a number of centuries before our era. As soon as methods were developed for separating iron from its ores in reasonably large quantities and at fairly low cost, it ceased to be classed as a precious material and began its career as the world's most valuable metal from the standpoint of actual use.

It is only since the time a man had learnt how to obtain and use metals and their alloys, he has been able to adapt his environment to his needs and desires. The present age is, in fact, the Age of Metals and it is important that we should have some acquaintance with these useful substances. In the ancient times, gold, silver, copper, tin, iron, lead and mercury were known as "The Seven Metals".

One other metal, zinc, has also been known in its role as one of the constituents of the alloy brass. Almost no metals other than these seven or eight were known until the eighteenth century and many that we use today, not until the nineteenth.

Metals are mostly solids at ordinary temperature and have comparatively high melting points with the exception of mercury. They are for the most part good conductors of heat and electricity, and silver is the best in these respects. They can be drawn into fine wires and hammered into thin sheets, characteristics that are called ductility and malleability, respectively. An ounce of gold can be drawn into a wire almost 50 miles long or hammered into a sheet that has an area of between 175 and 200 square feet.

From the point of tonnage produced and used, iron is the world's most common metal, followed in turn by copper, zinc, lead and aluminum.