The following question appeared in a physics degree exam at the University
of Copenhagen:
"Describe how to determine the height of a skyscraper with a barometer."
One enterprising 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 immediately.
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 verbally provide an 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 couldnıt make up his mind which
to use.
On being advised to hurry up the student replied as follows:
One, 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 = 1/2gt squared (height equals half times gravity time squared).
But bad luck on the barometer.
Two, 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 skyscraperıs shadow, and thereafter it is a simple matter
of proportional arithmetic to work out the height of the skyscraper.
Three, 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 = 3D 2 pi sqr root of l over g).
Four, if the skyscraper has an outside emergency staircase, it would be
easy to walk up it and mark off the height of the skyscraper in barometer
lengths, then add them up.
Five, if you merely wanted to be boring and orthodox about it, of course,
you could use the barometer to measure air pressure on the roof of the
skyscraper, compare it with standard air pressure on the ground, and
convert the difference in millibars into feet to give the height of the building.
Six, 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 janitorıs door and say to him ?I will give you this nice new
barometer, if you will tell me the height of this skyscraper.
The arbiter re-graded the student with an "A"