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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 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 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 sqrroot (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 Dane to win the Nobel prize for Physics.



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