2012年5月4日 星期五

給下一輪不平亂世領導者的物理考題

當了一學期助教,最後一件工作是出期末考題,我們的做法是由五個助教按專長各想幾個題目,然後與教授開會討論,決定最後考題的內容。

這是一門通識課,用台灣說法應翻成「科技與社會」,聽來很聳,但課的內容很充實,其實就是給非理工主修的大學生一個學習基本物理與相關科技的課程,台灣另有類似的課叫作「敘述性物理」,但我們的課不只是敘述性(也就是沒有方程式)的,還是得要求他們去算一些東西,例如火箭的脫離速度或者士力架巧克力棒裡含的能量等等。美國各大學也都有類似的課程,大家常戲稱這課叫開給詩人的物理課(Physics for poets),柏克萊稱之為「下一任總統必須知道的物理」,這也是我們這門課的非正式副標,因為老師常會說「我不是要教你們去發現新的物理或成為下一個蓋茲還是祖克伯,但有一天你要是當了總統,至少得知道…」

這四十幾位多半是我們稱為文科的學生,主修政治、社會學、語言學、哲學、歷史、文學、經濟或心理等等,坦白說我很難想像他們之中任何一位會成為未來的美國總統啦,也並不覺得這樣一學期的物理課足以在根本上改變什麼思維模式。

下面是我出的兩題簡答(選擇題比較無聊就不貼了),坦白說,在寫下這些題目時還滿有興致的。就我自己來說,只要這些小孩看到題目能會心一笑,並從中体會到一點透過科學看待這個世界的樂趣/美妙,也就很夠了。


1)      In ancient time, people held their view on force and motion based on the theories of Aristotle. In Aristotelian physics, every terrestrial object is made out of combinations of four substances, earth, fire, air, and water. Every object moves constantly to seek its “proper” location (called “natural” motion), until which it comes to rest, unless otherwise obstructed by what Aristotle called “violent” motion.


According to this model, the natural state of any object is rest (when it reaches its proper location). In addition, the heavier (“earthier”) object falls faster to the earth because it ‘strives harder” than lighter objects.

Now that you have learned Newton’s laws of motion as a more accurate paradigm, it’s your chance to look back in time and review the wisdom of the great philosopher.

a     (a)   Comment on Aristotelian theory of motion (focusing on the part in bold face) based on your  knowledge of Newton’s laws of motion. In order to get full credits, you are expected to spot the contradictions to Newton’s laws, and explain why they are wrong.


b    (b) For each of the refutation you make in part (a), give an example to support it. 

2)      After Mr. Whitman got bored enough in the lecture hall, where the learned astronomer ranged the proofs, the figures in columns before him, he glided out and wandered off by himself. The poet, in the mystical moist night-air, looked up in perfect silence at the stars, and noticed a couple of things.  “Hmmm, these stars, not only do they twinkle all the time, but they also come in different colors. I wonder why it is so?” marveled Mr. Whitman.

Now after one semester of (課名), it is your privilege to explain to Mr. Whitman why the learned astronomer was not talking about something completely dull or useless. In fact, you should now be able to show him that with deeper understanding of the physical world, you can enjoy far more beauty the world has to offer!

a    (a)Explain why Mr. Whitman could see stars of different colors, say orange, yellow, and blue. To simplify the discussion, let us assume the stars are perfect black bodies.

b    (b)To see the stars, our eyes have to catch the light emitted from the star. This light has to travel an extremely long distance (typically thousands of light years) and make its way through the atmosphere to reach us. Assume that the stars never changed its rate of emission with time, the space was in perfect vacuum, and the light was not obstructed by anything else before entering the atmosphere.
Explain why the star twinkle using what you learned about light and wave. Do the star at horizon twinkle more or less frequently? Why?

Hint:
Remember that atmosphere is a mixture whose composition changes dynamically, and thus its physical properties like temperature, thickness, density, and refractive index. 

(這題還請了知名插畫家愛金塔老師用ipad畫了示意圖,沒貼上就是了)

2 則留言:

WF 提到...

標題真有梗!

這題目對文科大學生來說似乎還有挑戰性的,真棒!

becco 提到...

呵呵,題目也有啊…

不過出題目有時還真的需要花精神,不是適合常做的事。