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可有大俠開(kāi)課講講英制與公制的起源和依據(jù)

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1#
發(fā)表于 2016-1-29 13:42:36 | 只看該作者 回帖獎(jiǎng)勵(lì) |倒序?yàn)g覽 |閱讀模式
In the gravitational systems, the weight of the mass unit (pound-mass) on Earth's surface is approximately equal to the force unit (pound-force). This is convenient because one pound mass exerts one pound force due to gravity. Note, however, unlike the other systems the force unit is not equal to the mass unit multiplied by the acceleration unit[8]—the use of Newton's Second Law, F = m·a, requires another factor, gc, usually taken to be 32.174049 lbm·ft/lbf·s2 = 32.174049 lbm/slug. "Absolute" systems are coherent systems of units: by using the slug as the unit of mass, the "engineering" FPS system avoids the need for such a constant. The SI is an "absolute" metric system with kilogram and meter as base units.; t4 y! l1 _( t* n( w3 S+ t
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                                                                                                                                                      -----From Wikipedia" ~5 E1 J7 k5 q' U4 i2 u! @" J
https://en.wikipedia.org/wiki/Pound_(force)#Definitions
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, x& t4 i3 x4 a1 I, k8 b以上是關(guān)于磅的相關(guān)內(nèi)容,。2 d/ _% g6 u: D# z* ^1 _' O' S3 m7 j
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聽(tīng)八爺講當(dāng)年俄國(guó)人造飛機(jī),,將單位改成米規(guī)英制,,其實(shí)質(zhì)是什么,?
5 F( _5 }4 k0 i1 g! u0 k在材料力學(xué)方面,,老美的教材要求學(xué)生掌握兩種單位,。  ]4 M9 I  L; P- ]; e- [) p
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A Careful Balance Between SI and U.S. Customary Units Is
7 u9 m! Z9 Z0 |5 o; Y# wConsistently Maintained. Because it is essential that students be( h; W+ U. D+ }+ p0 A
able to handle effectively both SI metric units and U.S. customary$ s) D9 k! Z; i7 L( Q
units, half the examples, sample problems, and problems to be- R! O# n4 b: o9 l  i
assigned have been stated in SI units and half in U.S. customary
7 Z( w+ D/ E4 b+ q, U' @8 C% runits. Since a large number of problems are available, instructors can
, s) I. T3 h' |3 Bassign problems using each system of units in whatever proportion
& E0 x5 J: D% fthey find most desirable for their class.
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——引自 MECHANICS of MATERIALS4 Y( `4 G0 R+ w- C4 g( l, b
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2#
發(fā)表于 2016-1-29 14:06:04 | 只看該作者
咱覺(jué)得吃飽撐著可以盡可能背誦數(shù)字,早期電話不普遍,高中時(shí)校內(nèi)某英文老師視力能見(jiàn)度只有一呎深,沒(méi)事拿起本市電話簿背誦,說(shuō)某戶姓名他能告訴你電話號(hào)碼,過(guò)幾年用戶大增隨之增位數(shù)就不管用了% @' [# k( [; v2 c
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你問(wèn)雨人4位數(shù)乘4位數(shù),他毫不思索說(shuō)出正確答案,因?yàn)樗?jiàn)過(guò)這數(shù)字
3#
 樓主| 發(fā)表于 2016-1-29 15:01:22 | 只看該作者
恁老廝 發(fā)表于 2016-1-29 14:06
$ b5 D$ X( c6 X: N咱覺(jué)得吃飽撐著可以盡可能背誦數(shù)字,早期電話不普遍,高中時(shí)校內(nèi)某英文老師視力能見(jiàn)度只有一呎深,沒(méi)事拿起本市 ...
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不錯(cuò)的引例哈
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