Chapter 1 Measurement第 1 章 測量

Chapter 1 Measurement1-1 What is Physics?

1-2 Measuring Things

1-3 The International System of Units

1-4 Changing Units

1-5 Length

1-6 Time

1-7 Mass

1-1 What is Physics?

• Science and engineering are based on measurements and comparisons.– Global Positioning System (GPS)

全球定位系統

1-2 Measuring Things

• We measure each physical quantity in its own units, by comparison with a standard.

• Base standards must be both accessible and invariable.

1-2 Measuring Things

• standard 標準• unit 單位• base quantity 基本量• derived quantity 導出量• base unit 基本單位• derived unit 導出單位

SI Base Quantities

• length 長度• mass 質量• time 時間• electric current 電流 • thermodynamic temperature 熱力學溫度

• amount of substance 物質量• luminous intensity 發光強度

1-3 The International System of Units

• International System of Units 國際單位制– SI (Système International) 國際單位制

• metric system 公制• scientific notation 科學記號、科學記法– 3.56 109 m– 4.92 107 s

10 進位倍數和分數符號 字首 符號 10 的次

方名稱 字首 符號 10 的次方 名稱

yotta Y 1024 佑 deci d 10-1 分 zetta Z 1021 皆 centi c 10-2 釐 exa E 1018 艾 ( 百萬

兆 ) milli m 10-3 毫

peta P 1015 拍 ( 千兆 )

micro µ 10-6 微

tera T 1012 兆 nano n 10-9 奈 ( 毫微 )

giga G 109 吉 ( 十億 )

pico p 10-12 皮 ( 微微 )

mega M 106 百萬 femto f 10-15 飛 ( 毫微微 )

kilo k 103 千 atto a 10-18 阿 ( 微微微 )

hecto h 102 百 zepto z 10-21 介 deka(deca) da 101 十 yocto y 10-24 攸

1-4 Changing Units

• conversion factor 換算因子、換算因數• significant figure 有效數字• decimal place 小數位、小數位數

1-5 Length

• In 1792, Republic of France established a new system of weights and measures.

• The unit of length, the meter, was defined as one ten-millionth of the distance from the north pole to the equator.

• International Bureau of Weights and Measures 國際度量衡局

• Standard meter bar– Platinum-Iridium bar

1-5 Length• In 1960, the meter was defined to be 165

0763.73 wavelengths of a particular orange-red light emitted by krypton-86 in a gas discharge tube.

• Krypton 氪• Gas discharge tube 氣體放電管

1-5 Length

• In 1983, the meter was defined as the length of the path traveled by light in a vacuum during a time interval of 1/299 792 458 of a second.

• The speed of light c is then exactly

c = 299792458 m/s.

Standard 標準• Base standards must be both accessibl

e and invariable.

• primary standard 原級標準、原標準• secondary standard 次級標準、副標準• order of magnitude 數量級

1-6 Time• Time has two aspects

–When did it happen?– What is its duration?

• Earth’s rotation• Quartz clock 石英鐘• One second is the time taken by 9199263

1770 oscillations of the light emitted by a cesium-133 atom.

• Atomic clock 原子鐘• National Institute of Standards and Techn

ology (NIST) 國家標準與技術研究院

10-hour watch

Variations in the length of the day over a 4-year period

1-7 Mass

• Carbon-12 atom

• atomic mass unit, u 原子質量單位1 u = 1.66053886 1027 kg

• Density, 密度• liquefaction 液化• quicksand 流沙

The international 1 kg standard of mass (platinum-iridium)

Uncertainty 誤差• Accuracy 準確度

– Accuracy refers to how close a measurement is to the true value.

• Precision 精密度、精確度– Precision in a strict sense refers to the repeat

ability of the measurement using a given instrument.