Technology and our changing world high Technology

Review questions

1. 
   How would you define “industry”?
   
2. 
   What is another word for industrial efficiency?
   
3. 
   What are the three essentials of industry?
   
4. 
   Define “Gross National Product”.
   
5. 
   What is high technology?
   

MEASUREMENT
How tall are you? Are you 5’ 6” or 1 35 meters? Are you taller or shorter than the student next to you? Your exact height can be found only by measuring. There are two kinds of measuring systems: the customary (inch) system and the metric system.
In all the activities in this book, you must be able to measure. This means you have to know how to read a rule. It is surprising that few people learn to read a rule in the inch system. Now many people must be able to read a metric rule, as well.
People have always needed to know the size of things. Hundreds of years ago this was difficult. There was then no standard of measurement. According to history, the Romans invented the inch. They decided that an inch was the width of agrown man’s thumb. There is astory thatking Alfred of England decided lhe length of the foot He said that a foot would be the distance from the heel to the toe of his own foot. He ordered a piece of iron cut to a length of three feet. It was to serve as a master yardstick, a standaid for the whole kingdom. From “standards” like these, the English, or customary, system ofmeasurementdeveloped.


The Metric System
In 1791, the French government adopted a standard of measurement called the metric system. This was based on aunit called the metric.
Today, the United States still uses lhe customary, or English, system of measurement. It is only major country that does so. Even the English have adopted metric. However, the United States is now on its way toward using metrics. In going so, we will adopt the SI “International System of Units,” the modern metric system of measurement.
There are seven base metric units. In beginning drawing you will need to know on ly about the metre.
Because we still use the customary system, many of the dimensions in this book are in inches or fractions of an inch. However, the metric system is also used by many companies. Thus, a system called “dual dimensioning” is sometimes used. This means that both the English and metric measurements aregiven. You should learn to read arule in both systems accurately.
The metric system is notdifficult. All thatyou need to know is 1hatwz7/z means one one-thousandth; centi means one one-hundredth; and kilo means one thousand. Because it is a decimal system, it is quite easy to learn. One inch equals 25.4 millimeters, or 2.4 centimeters. One meter equals 39.4 inches.
Most rules used in drawing are one foot., or twelve inches, long in the customary system. The measurements are usually given in feet, inches, and parts of an inch. You should not find it hard to measure feet in exact inches. You already know that there are twelve inches in a foot and three feet, or thirty-six inches, in a yard. In the metric system, measurement is even easier. There are ten millimeters in one centimeter, a hundred centimeters in one meter, and a thousand meters in one kilometer.
The distance between о and 1 is one inch. At line A the inch is divided into two equal parts. Each half is one - half inch (‘A”). On a rule, this half­inch division line is the longest line between the inch marks. At line В the inch is divided into four equal parts. The first line is the second line is ²/₄”, or !A “; the third line is ³/₄ “. At line C, you will notice that the inch is divided into eight equal parts so that each small divided is ¹ /₈”. Two of these divisions make ²/₈”, or !4”(as shown on line B). Four of these divisions make ⁴/₈”, or ²/₄”, or ‘А”. At line D, the inch is divided into sixteen parts. Each paid is 7₁₆”. This is usually the smallest division found on rules used in drawing. Notice again that ⁴/₁₆” is equal to, ²/₈”, or One line past %” is equal to ⁵/_l6”. You will see on your rule that between each one-inch mark, the half­inch mark is the longest one. The quarter-inch mark is the next longest and die eighth-inch mark thenext. The six teen th-in ch mark is theshortest.
To read apartor fraction of an inch, count the number of small divisions beyond the last inch mark. For example, when measuring the line, you will find that it is 2” plus four small divisions. This is ⁴/|₆, which is the same as ²/₈”or The line measures 2 !4”. One small division past 14 ” would be⁹/i₆” (⁸/₁₆”+'/₁₆”).
Now let’s look at a metric rule. Here you see that the rule is divided into millimeters. Ten millimeters equal one centimeter. Most shop measurements are in millimeters.
Measure the line with a metric rule. The line is 47 millimeters long. For more practice, measure the lines.