by / Monday, 28 July 2014 / Published in Uncategorized


A student at university was required to describe how to determine the height of a skyscraper with help of barometer. The student replied, “Tie a long piece of string to the neck of the barometer and lower the barometer from the roof of the skyscraper to the ground. The length of the string plus the length of the barometer from the neck down should equal the height of the building.”

Needless to say, the student was failed without much ado.

The student appealed, stating that his answer was technically correct. The university was constrained to appoint an arbiter to adjudicate the result. The arbiter concurred that answer was technically correct, even if it did not display any knowledge of physics. To resolve the matter, he gave the student six minutes for a viva voce examination, calling upon him to show that he did possess some minimal understanding of the underlying principles of Physics.

The student was still pondering about the question as time began to run out. When the arbiter prompted him to hurry lest he failed the viva voce, the student replied as follows:

1. Well, for starters, you could take the barometer up to the roof of the skyscraper and drop it over the edge and measure the time it takes to reach the ground. The height of the building can then be computed by simple formula H=0.5gxt^2, if you are willing to write off the barometer.

2. Alternatively, if the sun is shining brightly, 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.

3. Again, if the skyscraper has an external emergency staircase, it would be easier to walk up marking the height of the skyscraper in barometer lengths, then adding them up.

4. If however you wanted to be boring and orthodox about it, you could use the barometer to measure the air pressure on the roof of the skyscraper and then on the ground, and convert the difference in millibars into feet to figure out the height of the building.

5. But if you wanted to be scientifically fastidious 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 standing on the roof of the skyscraper. The height may be worked out by the difference in the gravitational restoring force T=2π√l/g.

6. But if you don’t want to apply any scientific methods, undoubtedly the best way would be to knock on the janitor’s door and say to him, “I will give you this nice new barometer if you tell me the height of this skyscraper”.

After he had spouted all the answers, the arbiter asked the student, ‘You did know the answer the professor wanted from you, didn’t you?”…..The student replied, ‘Of course I did, and I just don’t like people telling me how to think.’ The student was Neils Bohr, and that is scientific temper indeed!!!

“NEVER EXPRESS YOURSELF MORE CLEARLY THAN YOU THINK”- Bohr                                         



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