Thinking outside the box: the barometer question

BarometerThis is a short story on thinking outside the box. In a physics exam at the University of Copenhagen, the students were asked how to measure the height of a skyscraper using a barometer. One of the students suggested that you go up on the rooftop, tie a string to the barometer and lower it down to the ground and then measure the length of the string. The professor gave the student zero points on the question with reference to the fact that with his answer he did not demonstrate any knowledge of physics. The student complained with the motivation that the answer was obviously correct and, after some arguments, he was given the opportunity to provide an alternative solution to the problem. The student thought for a long while without answering. The professor who thought the student had no idea became more and more annoyed and demanded a quick response. The student then answered that there were so many solutions to the problem that he did not know which one he would choose but then he said:

First, you can once again pick up the barometer to the roof drop it over the edge and with a chronometer measure how long it takes for the barometer to hit the ground. Using the formula x = gt square / 2, you can then calculate the height of the building. But that solution would not be particularly good for the barometer …

Or you can place the barometer vertically in the sun and measure the length of its shadow. If you then measure the length of the building’s shadow, you can easily determine the height of the building based on the principle of two uniform triangles. But of course, it requires that the sun shines and that you do not measure the height of a building on the equator in the middle of the day …

A more direct method, assuming there is a fire ladder outside the building, is to climb the stairs while marking the height of the barometer along the wall. You can then count the number of marks and multiply by the height of the barometer. But this requires a lot of time and a good energy …

If you want to be more sophisticated, you can tie the barometer on a string and swing it as a pendulum and determine the value of gravity at street level and at the top of the building. Based on the difference between the two values, you can calculate the height of the building.

If you want to be really boring and orthodox you can of course use the barometer to measure the air pressure on the roof of the skyscraper and on the ground and, on the basis of the difference, calculate the height of the building. But this answer is so obvious that I did not even consider mentioning it.

Because we were invited to think for ourselves, the solution that would appeal most to me is to take the barometer to the property manager and tell him that he can get a nice barometer if he tells how tall the building is.

According to legend, the student was Niels Bohr, the first Danish scientist to be awarded the Nobel Prize in Physics.

Tip: When facing a problem, do not be satisfied with the first and most obvious solution. It may not be the best, and it is always an advantage to be able to choose from several different options. Reflect a moment on alternative solutions. Dare to be wild, crazy and think differently. The most creative solutions often come first when you have already came up with the more conventional ones. And perhaps most importantly, never be self-critical in the problem-solving phase. It’s only when you have a range of options that you should sit down and choose the best.​


Author: Karl Ekdahl

International public health leader and creativity blogger.

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