The following concerns a question in a physics degree exam at the University of
Copenhagen:-
"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 answer so incensed the examiner that the student was failed immediately. He
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 wasdecided to call the
student in and allow him six minutes in which to providea 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 sq rroot (l / g).
Or if the skyscraper has an outside emergency staircase, it would be easierto
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 intofeet 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'."
Some claim that the student was Niels Bohr, the only Dane to win the Nobel prize for Physics.