Bridges

Bridges are a natural part of everyday life. A bridge provides passage over some sort of obstacle: a river, a valley, a road, a set of railroad tracks, etc.

The type of bridge used depends on various features of the obstacle. The main feature that controls the bridge type is the size of the obstacle. This is a major factor in determining what type of bridge to use.

The biggest difference between the three is the distances they can cross in a single span. A span is the distance between two bridge supports, whether they are columns, towers or the wall of a canyon.

Each bridge type deals with two important forces called compression and tension: Compression is a force that acts to compress or shorten the thing it is acting on. Tension is a force that acts to expand or lengthen the thing it is acting on. A simple, everyday example of compression and tension is a spring. When we press down or push the two ends of the spring together, we compress it. The force of compression shortens the spring. When we pull up or pull apart the two ends, we create tension in the spring. The force of tension lengthens the spring.

A suspension bridge is one where cables (or ropes or chains) are strung across a river (or whatever the obstacle happens to be) and the deck is suspended from these cables. Modern suspension bridges have two tall towers through which the cables are strung.

TEXT #13

1. Read and translate the text

2. Vocabulary exercises

3. Grammar exercises

4. Speaking tasks

The central event of our time

It is among the white youth of the world that the greatest change is taking place. It is they who are experiencing the great psychological pain of waking up to find their respectable heroes turned by events into criminals. Communication and understanding between the older and younger generations of whites has entered a crisis. The elders, who, in the tradition of privileged classes or races, are trapped by old ways of thinking and blind to the future, have only just begun to be displeased — because the youth have only just begun to rebel. So thoroughgoing is the revolution in the minds of white youth that the traditional tolerance which every generation has more or less displayed is quickly exhausted, leaving mutual misunderstanding, hostility, and contempt.

The national liberation movements of the oppressed peoples of the world, along with the Negro rev­olution in America, have become the central event of our era and opened the way to a new evaluation of history: a re-examination of the role played by the white race since the beginning of European expan­sion. The positive achievements of the European nations are also there in the record, and future genera­tions will praise them. But the positive aspects are outweighed by the negative. Slave-owners, murderers, invaders, oppressors— the white heroes have acquired new names. The great white statesmen whom school children are taught to respect are revealed as the architects of systems of human exploitation and slavery. Religious leaders are exposed as defenders and justifiers of all these very bad acts. Schoolteachers and college professors are seen as a group of brainwashers and whitewashers.

The white youth of today are coming to see clearly that to escape the burden of the history their fathers made, they must face and admit the moral truth concerning the works of their fathers. That all the presidents up to Lincoln led a slave state and that every president since Lincoln neglected the issues affecting the human rights and general welfare of the broad masses_< of the American people weigh heavi­ly upon the hearts of these young people.

TEXT #14

1. Read and translate the text

2. Vocabulary exercises

3. Grammar exercises

4. Speaking tasks