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標(biāo)題: 可有大俠開課講講英制與公制的起源和依據(jù) [打印本頁]
作者: 趙辛楣    時間: 2016-1-29 13:42
標(biāo)題: 可有大俠開課講講英制與公制的起源和依據(jù)
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.
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% F6 C6 W3 ~* b. R& Y2 A9 G                                                                                                                                                      -----From Wikipedia# @$ s/ I+ G  K# ]2 R7 N7 [: l1 C
https://en.wikipedia.org/wiki/Pound_(force)#Definitions; b) f% W  Y6 {

+ a8 ]0 d+ P1 B* l# y3 L& l以上是關(guān)于磅的相關(guān)內(nèi)容。
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聽八爺講當(dāng)年俄國人造飛機(jī)，將單位改成米規(guī)英制，其實(shí)質(zhì)是什么？
0 Y' i- c: v% N/ [3 K9 q在材料力學(xué)方面，老美的教材要求學(xué)生掌握兩種單位。& B2 Y; P/ i5 D4 J# k

9 A$ N  Z- u# z% E7 R7 jA Careful Balance Between SI and U.S. Customary Units Is
- O1 B/ T& l3 `6 E$ lConsistently Maintained. Because it is essential that students be
* M" m: h9 Q' S% E- ~able to handle effectively both SI metric units and U.S. customary7 Q! T. A, S% o4 q
units, half the examples, sample problems, and problems to be
5 R9 N/ l2 \. z' Zassigned have been stated in SI units and half in U.S. customary  ?, A2 Z- v) e* S
units. Since a large number of problems are available, instructors can
/ o- b# P6 t' t2 {! t! u& Yassign problems using each system of units in whatever proportion
: E, f' P) W8 \* B2 F/ d' Vthey find most desirable for their class.1 }+ Z! x6 g5 ~# C- C
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——引自 MECHANICS of MATERIALS
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作者: 恁老廝    時間: 2016-1-29 14:06
咱覺得吃飽撐著可以盡可能背誦數(shù)字,早期電話不普遍,高中時校內(nèi)某英文老師視力能見度只有一呎深,沒事拿起本市電話簿背誦,說某戶姓名他能告訴你電話號碼,過幾年用戶大增隨之增位數(shù)就不管用了* K& }: l8 @# _6 k" j

: c: V9 o9 W4 P, |: V你問雨人4位數(shù)乘4位數(shù),他毫不思索說出正確答案,因?yàn)樗娺^這數(shù)字
作者: 趙辛楣    時間: 2016-1-29 15:01
恁老廝 發(fā)表于 2016-1-29 14:06
  G/ o* w3 @2 T5 A; `咱覺得吃飽撐著可以盡可能背誦數(shù)字,早期電話不普遍,高中時校內(nèi)某英文老師視力能見度只有一呎深,沒事拿起本市 ...
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不錯的引例哈: R2 b5 B3 {9 I9 ?1 w9 D2 f& v




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