水草情迷

搵個舊post都搵到點解
想請教各位前輩!!
thx

你打錯字囉, 係 "虹吸" 呀, 即係水向低流, 隻隻濾桶都係用呢個原理的啦.

好似叫虹汲
將要入既水放高過魚缸,將注滿水既水管放入魚缸,位能差將水抽入缸中

原本來係咁~
唔該哂你地

應該係大氣壓力將水壓入魚缸

_________________
http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

是利用位能差(Potential Energy Gradient)來將水引入水缸呢!
當物質於較高位置, 佢就有較高能量...就會向低處流放出能量...
水向低流就係咁原理喇!!

哈..唔識得點答你好..
不過算啦~你指物質o係較高位置有高能量..
o係低位置其實都係有咁多能量..
(要假設能量冇流出哩個系統先..)
因為位能會轉去動能嘛~^ ^~

但如果o係真空度做..水高去水底哩個"道理"..
應該唔會實行..

_________________
http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

只要有重力
就自然會有水高去水低
而真空只會好快咁蒸發d水,吾會影響虹吸作用

佩服佩服!
我明白我的理論錯了 ...虹吸是一定要有大氣壓力的!!
事因我都網上找了一些reference參考!!
多謝指教!!
以下是其中一編
http://en.wikipedia.org/wiki/Siphon

死啦~我都問過教我phy o既阿sir呀~
同大家分享o下先~我未係好明阿sir講乜~哈哈~
不過我講果一套都好似未係完全正確~
但可以肯定o既係..utopia講o既係o岩o既..
就係真空狀態下..水會好快蒸發..

以下係phy阿sir回覆我e-mail o既答案..仲有我o既問題~

阿sir呀..想問o下你呢..水向底流哩個係人人都知o既道理..
但o係真空狀態下又會唔會實現呢..!?
有人提出高水有高位能..所以會向下流動..

如果設計一個實驗..放一盤水o係高處..
然後用一條注滿水o既管"引水"..
唔知會唔會都係向底流呢..!?
(假設水管o係盤入面係o係最低處..而出水口亦o係同一個水平..
以至壓力平衡..)

ps.真空狀態下冇大氣態力..咁水係咪會定住o係果度..!?

因為屋企做唔到真空態..所以做唔到實驗..如覺得問題愚蠢..見諒~^ ^~

阿sir o既回覆:
1. The common sense you mentioned is a result of potential. You know, water
at high level has potential energy. Hence it trends flowing to low level.
2. Potential is due to the effect of gravity. Gravity still exists even in
vacuum, e.g. gravity on the earth by the sun transimits through earth-sun
space.
3. The answer for your second question is "yes". (Reason same as above.)
4. You can't test for the assumption because "same level" is only drawn from
a rough sense. So, it's chance to observe water coming out.
5. Actually, no vacuum observe if there is water present. Because water will
evaporate even in vacuum.
WTP

ps.好鐘意今次o既討論~好開心~得著唔少~
期待有下一次~

_________________
http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

我相信你阿sir既答案都正確...
但因為你都無表明問緊佢虹吸的問題, 所以佢並不是回答虹吸的理念.
因為虹吸意思是液體經過管道, 先向上流再向下流去一處比較低的地方 (見附圖), 而你所詢問的只是關水向底流的問題...

根據我上面的參考資料顯示...
http://en.wikipedia.org/wiki/Siphon
虹吸是需要大氣壓力的. 而不同的大氣壓力會影響虹吸可上升的高度...例如在正常大氣壓力下, 水可以攀升近10米!!
Once started, a siphon requires no additional energy to keep the liquid flowing up and out of the reservoir. The siphon works because the ultimate drain point is lower than the reservoir and the flow of liquid out the drain point creates a vacuum in the tube such that liquid is drawn up out of the reservoir.

The maximum height of the intermediate point (the crest) is limited by atmospheric pressure and the density of the liquid. At the high point of the siphon, gravity tends to draw the liquid down in both directions creating a vacuum. Atmospheric pressure on the top surface of the higher reservoir is transmitted through the liquid in the reservoir and up the siphon tube and prevents a vacuum from forming. When the pressure exerted by the weight of the height of the column of liquid equals that of atmospheric pressure, a vacuum will form at the high point and the siphon effect ended. For water at standard pressure, the maximum height is approximately 33 feet (10 m); for mercury it is 30 inches (76 cm).
此文章另外一段則說, 很多科學家都研究為何水會在虹吸管向上攀升, 亦有人提出在真空狀態下仍然會有虹吸現象. 但在實際上, 是要依靠大氣壓力的.
Among some physicists there is some dispute as to what causes the siphon to lift liquid from the upper reservoir to the crest of the siphon[3] (http://www.straightdope.com/columns/010105.html). They argue that theoretically, internal molecular cohesion is sufficient to pull the liquid up the intake leg of the siphon to the crest. Furthermore, some argue that theoretically a siphon will operate in a vacuum. In practice atmospheric pressure is required.

如果大猩猩王不介意的話, 可以用此資料再和你阿sir討論...再大家一齊研究呢!!
我都好開心有此討論, 得益不少!!

哈哈~其實個網都答哂要問o既o野嚕~
因為近排阿sir就係教緊壓力果一堆o野~
所以先會有哩個問題o者~^ ^~

_________________
http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

證明你concept 無錯, 考試一定掂!!

唉..最慘就係我淨係得o的concept正確..
唔識計數果o下衰呢..哈哈..

_________________
http://www.aqugrass.com/phpBB2/viewtopic.php?t=39365
我的魚缸資料(2008-5-13更新)

~唔該哂CrabJai同大猩猩王~兩位呀
小弟完全明白哂