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 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 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.
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