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"Describe 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 university appointed an independent 
arbiter to decide the case. The arbiter judged that the answer was 
indeed correct, but did not display any noticeable knowledge of physics. 
To resolve the problem it was decided to call the student in and allow 
him six minutes in which to provide a verbal answer 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. The arbiter reminded him that time was running out, to which 
the student replied that he had several extremely relevant answers, but 
couldn't make up his mind which to use.

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 restoring 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."

"If you merely wanted to be boring and orthodox about it, of course, you 
could use the barometer to measure the air pressure on the roof of the 
skyscraper and on the ground, and convert the difference in millibars 
into feet to give the height of the building."

"But since we are constantly being exhorted to exercise independence of 
mind and apply scientific methods, undoubtedly the best way would be to 
knock on the janitor's door and say to him '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 to win the 
Nobel prize for Physics.