急求-有關地鐵要黃線(bernoulli”s principle)既有關實驗!

This principle finds its major application in airplane and it explains why airplane can fly. So if you want to know more of this principle, you can look for Physics books (AL or undergrate level).

However, does your essay have to be related to physics discipline? Otherwise I suggest you need to consider to approach your essay in another direction.

I think when MTR put the yellow lines on each platform ages ago, they did not consider any physics theory. Probably, their considerations are manily on passenger behaviour, safety and past experience. For example, when passengers standing too close to the platform edge, they may fall down accidentally or easily knock down by someone. This is more of common sense and experience of Operating staff, rather than related to Newton law of gravitation !

Their considerations for reminding people to stand behind the yellow line are :

- passenger may fall down the track easily

- passenger or stuff that he/she carries may be hit by an oncoming train

- yes indeed passenger may be dragged by air and hit the train when train is passing through a station (you can support your point by using bernoulli principle)

I think unless Physics is the main theme for your essay, I suggest to approach this essay using may be Psychology, e.g behaviour, motivation, memory -- focusing on crowd control, and that people need constantly remind of important rules.

Other background info.

Station control, such as this yellow line, should be within the scope of Operating department 車務部, i.e. those people you see in the station and their bosses. They are not technical staff and require no science background. In fact, in the early days, most their staff (even senior ones) are F.5 or at most F.7 graduates and they work their ways up by their experience.

Also, you can try to contact MTR PR see if they can give you some help on this issue (though quite unlikely)

Hope this can help.

科普節目《流言終結者》曾做過火車高速駛過月台的實驗（他們借了一台火車頭，並用它以高速通過月台前的路軌，測試月台上的假人會否被吸到列車處），結果發現此流言不實，實驗中的假人並無被吸到列車處，而只是被吹倒（至少在現實中，事實的確如此）。

不用感到失望，你的功課並非做無可做！你仍然可以計算一下列車把人扯出來的最少力量以証明氣流並不是設計黃線的最重要考量！

首先，我建議你証明列車的確能產生把物件吸入的氣流，這需要一個風洞（測試飛機模型那種，沒有的話試著用膠片配著風扇（製風）和吸管（作蜂窩狀穩流器）自製吧！）和一個列車模型（越大越好），用吹進去的煙表示列車行進時產生的氣流（也有機會是旋渦）。

之後，透過計算，算出列車在不同速度行駛時所產生的低壓，當中所產生的力量又能否把人（就當是一個小孩吧）拖到車箱處。

再來，計算那種速度的列車所產生的力能把人拖到車箱處，導致傷亡（小心計出了個大於音速的數，列車不會用音速埋站的），完成

老實講, 我唔明你上面寫既定律係講乜, 但以前睇電視聽過一個咁既理論。(只是大概意思, 因為太耐, 唔係太記得全部內容)

話說, 一個正常空間本身滿怖相同而平均既空氣粒子, 若其中某部份空間既空氣粒子突然變稀少, 那部份既外圍空氣粒子就會自動填補, 而呢個填補過程就會產生動力將周邊既空氣粒子推向稀少空間, 形成「拉扯」, 就好像一灘水, 若係吸去中心部份的水, 其他水份子就會向中心方向慢慢移動, 慢慢「填」回那缺水位置。

最記得那時電視做了一個簡單實驗, 那是主持人手執一條幼長軟紙條, 然後問身旁的人, 如果在紙上面順著紙條角度吹一口氣(即假設主持人水平線般拿著一條紙條, 末端由他自然垂下, 並放在下唇位置), 那紙條會有何變化? 當時有人表示紙條會更向下彎, 但結果卻是, 紙條緩緩升起, 最後, 主持人說若紙條是超越黃線的人, 那口氣是代表列車在到達時逼開的空氣粒子, 我們便清楚看到超越黃線的人的危險。

至於為何列車駛來時, 前方的空氣粒子會變得稀薄, 那要看你對物理科的知識了。

2008-05-27 16:45:32 補充：
那簡單實驗, 用一張20元紙幣也可試到, 但一定不要有太強的摺痕