Man and his machines
Date: 2015-10-07; view: 456.
Answer the following questions.
Match the terms with their definitions.
| 1. linear motion 2. reciprocating motion 3. rotary motion 4. oscillation motion 5. intermittent motion 6. irregular motion | a) the motion of an object around an internal axis b) a repeating fluctuation in a physical object or quantity c) the body moves so that every particle of it follows a straight-line path d) stopping and starting at irregular intervals e) not occurring at expected or equal intervals f) motion alternately backward and forward, or up and down |
1. What are mechanisms used for?
2. Can any machine be looked as a group of interconnected mechanisms? Why?
3. What are the basic types of motions for mechanisms?
4. What is linear motion?
5. What is rotary motion? How is it measured?
6. What is intermittent motion?
7. What is reciprocating motion? How is it measured?
8. What is oscillation? How is it measured?
9. What is irregular motion?
10. What is the most basic motion of all motions?
Student independent study:
Now in all his activities man makes use of a multitude of machines. Although most of these are of quite recent origin, a few simple ones have come down from very ancient times. The bow and arrow were well known to prehistoric man, as he gained his food, and this “machine” was his tool in the struggle for existence. The wheel is also of prehistoric origin. The inclined plane and its uses have also long been known. Egyptian slaves lifted the huge stones that went into the construction of the great pyramids.
There was little change in the number of kinds of machines in use for nearly twenty centuries. But then as one new device after another came to displace others that were less efficient, the development speeded up. The railroad train did not long remain the only means of rapid transit. Soon the automobile appeared. The latest and speediest type of conveyance was limited neither by rails not by highways. It took to the air. In the country the days of the wooden plow have passed. The development of tractor made way for the use of a combine. By means of agricultural machines the farmer can not only give much more produce than ever before, but do it much more easily. This has been greatly facilitated by the rapid extension of electric lines. Now electric motors instead of muscle power operate the machines.
Perhaps the greatest advancement since old times has been achieved in the art of communicating ideas – the telegraph, television, telephone and radio.
The machine has also come to occupy a conspicuous place in the home. The electrically heated iron, the vacuum cleaner, refrigerator and many others have relieved the housewife of many physical cares and inconveniences.
Thus the machines that have developed in the last hundred years have completely transformed our life.
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