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当被问及到用一个气压计，如何来测量摩天大楼的高度时，一名学生这样回答："拴一根长线在气压计的颈上，然后把它从楼顶一直放到地面。绳子的长度加上气压计的长度就是摩天大楼的高度。'’ 看到如此简易的答案，老师怒火中烧，于是没让那个学生及格。但这名学生认为答案本身的正确性根本就无可辩驳，于是这所大学委派了一名仲裁去处理此事。仲裁者判定答案显然正确，但他也决定把那个学生喊进去，要他在六分钟内提供一份口头答案，至少要和物理学基本原理套上些关系。 足有五分钟，学生都坐在那里眉头紧锁地沉思着,一句话没说。仲裁建议他快点，于是学生便做出如下的回答：“首先，可以把气压计拿上楼顶，把它从楼角丢下去做自由落体,测量它落到地面的时间。楼的高度就可以套用公式：H=0.5gt2。不过气压计就碎了。” “或者如果有太阳的话，可以先测气压计的长度,把它立起来，测量它影子的长度。再测量大楼影子的长度，就可以通过比例方程计算出大楼的高度。” "但是如果想更学术一点的话,就可以用短绳系住气压计,之后使它做钟摆运动：先在楼下地面，再在楼顶摇摆它。根据童力回复力公式T=2tt根下l/g，比较两次的差异（周期和重力加速度），大楼的高度就可以通过计算得出。’’ “或者这座大楼外面有紧急情况时使用的楼梯，更简单的方法是走上去，用气压计分段量出大楼的高度，然后把他们加起来。” “然而，最好的方法就是直接去敲守门人的屋门，然后说‘这个气压计很精密很新，如果你想要我就给你。不过请麻烦告诉我大楼的高度。’” 这名学生就是尼尔斯•玻尔，诺贝尔物理学奖在丹麦的唯一获得者。 Great Moments in Physics When being asked how to determine the height of a skyscraper with a barometer, one student replied：“You tie a long piece of string to the neck of the barometer, then lower the barometer from the roof of the skyscraper to the ground. The length of the string plus the length of the barometer will equal the height of the building. ” This highly original answer so incensed the examiner that the student was failed. The student appealed on the grounds that his answer was indisputably correct, and the univer¬sity appointed an independent arbiter to decide the case. The arbiter judged that the an¬swer was indeed correct, but he decided to make the student provide a verbal answer in six minutes which showed at least a minimal familiarity with the basic principles of physics. For five minutes the student sat in silence, forehead creased in thought. On being advised to hurry up the student replied as follows： “Firstly, you could take the barometer up to the roof of the skyscraper, drop it over the edge, and measure the time it takes to reach the ground. The height of the building can then be worked out from the formula H =0.5g x t squared. But bad luck on the barometer. ’’ “Or if the sun is shining you could measure the height of the barometer, then set it on end and measure the length of its shadow. Then you measure the length of the skyscraper’s shadow, and thereafter it is a simple matter of proportional arithmetic to work out the height of the skyscraper. ’’ “But if you wanted to be highly scientific about it, you could tie a short piece of string to the barometer and swing it like a pendulum, first at ground level and then on the roof of the skyscraper. The height is worked out by the difference in the gravitational re¬storing force T = 2 pi sqroot (l/g). ” “Or if the skyscraper has an outside emergency staircase, it would be easier to walk up it and mark off the height of the skyscraper in barometer lengths, then add them up. ’’ “But undoubtedly the best way would be to knock on the janitor's door and say to him 4 If you would like a nice new barometer, I will give you this one if you tell me the height of this skyscraper. ’’ The student was Niels Bohr, the only person from Denmark who wins the Nobel prize for Physics. |
