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1. Measurements

1. Measurements. Dept. Phys., Tunghai Univ. 為什麼要學物理？為什麼要研究物理？. 衝破知識的高牆，調查宇宙的真相. 物質的基本組成是什麼？ 物質間的交互作用是什麼？. 測 量. 人是萬物的尺度 。. Protagoras (490~420 B.C). 訂定 基準 ： Standard. 與基準比較： Comparison. 基本的測量與單位. Length: Meter. Time: Second. Mass: Kilogram. Mass: Another Definition.

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1. Measurements

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  1. 1. Measurements Dept. Phys., Tunghai Univ.

  2. 為什麼要學物理？為什麼要研究物理？ 衝破知識的高牆，調查宇宙的真相 物質的基本組成是什麼？ 物質間的交互作用是什麼？

  3. 測 量 人是萬物的尺度。 Protagoras (490~420 B.C)

  4. 訂定基準：Standard 與基準比較：Comparison

  5. 基本的測量與單位 Length: Meter Time: Second Mass: Kilogram Mass: Another Definition It is the carbon-12 atom, which, by international agreement, has been assigned a mass of 12 atomic mass units (u). The relation between the two units is

  6. 幹嘛搞得這麼複雜？ • 因為測量必須….. • 跟誰去量無關 • 跟在哪裡量無關 • 跟在什麼時候量無關 • 怎麼量? • 定義一個「單位」，作為測量的基準 • 將帶測量的量與此基準比較，訂出其倍率 • 看起來很合理，不過得在特定的前提下才會成立

  7. Isaac Newton: 1642~1727 • The space is homogeneous （空間是均勻的） • The space is isotropic（空間是均向的） • The time is homogeneous（時間是均勻的） • The time is isotropic（時間是均向的） 這是什麼碗糕？

  8. 數量級：Order of Magnitude • 將數字以科學記號表示 A= a×10b, A的數量級 O(A) = b • A=2.5×103, B=8×10-6, O(A)=3, O(B)=-6 • 由於「數量級的概念」只是要概略估計數字的大小，以上面的例子B=8×10-6 ~10-5, 所以說 O(B)=-5 也是對的 • 費米：一個物理學家不管處理多困難的問題，都應該能在一個信封的背面算出答案的數量級 Enrico Fermi 1901~1954 1938 Nobel Prize

  9. 10-15 10-2 10-4 10-7 10-9 30m 40m 10-5 Taipei 101: 508m 10-10 10-1 18m 10-3 10-8 100

  10. Galaxy ~ 1021 m or 100000 Light Year Sun ~ 109 m Taiwan: 105m Earth ~ 107 m Virgo Cluster ~ 1023 m Or 10 M Light Year Solar System ~ 1013 m

  11. Not exact, but good enough

  12. It is the carbon-12 atom, which, by international agreement, has been assigned a mass of 12 atomic mass units (u). The relation between the two units is

  13. SI 制：現行國際標準單位系統

  14. Changing Units • Use “chain-link conversion” • Example: • 1hr/3600sec = 1 • 1kilometer/1000meter = 1 • Any quantity multiplied by these “1” won’t be changed • Convert 300km/hr to the unit of m/sec:

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