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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
1-5 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
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