[問題] 牛頓當初是用演繹還是歸納發現第二定律的?
※ [本文轉錄自 Physics 看板]
作者: harry901 (forcing to A cup) 看板: Physics
標題: [問題] 牛頓當初是用演繹還是歸納發現第二定律的?
時間: Thu Apr 22 23:03:30 2010
Newton's 2nd law states that F=ma.
這個簡單的東西當時牛頓是怎麼發現的? 是用演繹 還是歸納?
牛頓並沒有完全定義質量與力 他曾經說過以下
"Mass" and "Force" were not well-defined in Newton's work. "So far, my object
has been to explain the sense in which certain words little know are to
be used in the sequel. Time, space, and motion being words well know to
everybody, I do not define."-Issac Newton. see Ref.
當時他只知道運動的量是與速度跟質量(物質)有關
因此由演繹法: 定義動量(運動的量)P=mv P'=mv'=ma=F for a body(mass,matter)
當那顆蘋果掉下來之後 他是如何得到F=ma的? 或者說他是如何定義F?
由歸納法也可得:藉由觀測知道有一個東西主宰運動狀態的改變 假設叫做F
而這個F對於同一個body會產生正比的運動狀態 於是F~kma
由實驗歸納可得F=ma for k=1
那麼F=ma當時在牛頓的發表過程，是歸納還是演繹? 怎麼來的呢?
或者牛頓只知道F~kma這東西?
以下的Trick.來自於Ref.
""到目前為止只有長度被用來定義空間，時間，質量與力就現代物理學還是沒辦法
完全被好好定義，只是我們先限於牛頓力學的基礎而接受了時間，質量，力。""
Reference.
Foundations of Physics by R.B. Lindsay & H. Margeau, Dover Publications Inc.,
New York, 1957.
The Science of Mechanics by E.Mach,p.271,1960.
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04/23 17:16, , 15F
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04/23 17:17, , 16F
04/23 17:17, 16F
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04/23 17:18, , 18F
04/23 17:18, 18F