# The Naked Scientists Forum

### Author Topic: Barometer  (Read 4723 times)

#### cuso4

• Angel Delight
• Sr. Member
• Posts: 422
##### Barometer
« on: 09/12/2003 08:30:49 »
This is a story about a physic student.

He was doing an exam at the end of his physics degree and one of the question was "How do you measure the height of a skyscraper using a barometer?" This student wrote, "Tie a string onto the barometer and lower it from the top of the skyscraper and the height of the skyscraper is the length of the string plus the length of the barometer." And (not surprisingly) this student failed his physics exam!

But this student claimed there's nothing wrong with his answer so he wrote to the examiners who later reply, "The answer showed absolutely no understanding of physics at all. However we would like to meet you and ask for an oral response to the question."

During this student's oral exam, he gave another answer to the barometer question. He said, "You could stand on top of the skyscraper, drop the barometer and measure the time taken to reach the ground. Using the mass of the barometer, acceleration due to gravity and time taken to reach the ground, the distance travelled can then be calculated." The examiners were shocked. He went on, "Or better still, you could go to the janitor of the skyscraper and say he can have a new barometer if he can just tell me the height of this skyscraper"

There are rumours saying that the physics student in this story was Neils Bohr who later got a Nobel Prize for Physic [^]

Angel

"Anyone who has never made a mistake has never tried anything new." -Albert Einstein
« Last Edit: 28/12/2003 20:41:25 by cuso4 »

#### Solvay_1927

• Sr. Member
• Posts: 383
##### Re: Barometer
« Reply #1 on: 20/10/2005 01:52:02 »
Just came across the above (old) posting, and I've got another (extended) version of the same story.
But does anyone know whether this really was Neils Bohr, or is that just an urban legend?

The following is a question on a physics 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 he failed the student who immediately appealed on the grounds that his answer was indisputably correct.

The university appointed an independent arbiter to decide the case.

The arbiter ruled that the answer was indeed correct, but did not display any noticeable knowledge of physics. 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: "First, 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 this formula I have worked out for you on my text paper here."

Then the student added, "But, Sir, I wouldn't recommend it. Bad luck on the barometer."

"Another alternative", offered the student, "is this: 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 geometry to work out the height of the skyscraper. On the paper is the formula for that as well."

"But, Sir, 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 a gravitational formula, which I have determined here this time on a long sheet of paper with a very long and complicated calculation."

"Or, Sir, here's another way, and not a bad one at all. 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."

"But if you merely wanted to be very boring and very orthodox about the answer you seem to seek, of course, you could use the barometer to measure the air pressure on the roof, and on the ground, and then 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 ever to win the Nobel Prize in physics.

"Eagles may soar, but weasels don't get sucked into jet engines."

#### AlphBravo

• Full Member
• Posts: 65
##### Re: Barometer
« Reply #2 on: 31/10/2005 08:11:51 »
So is then the correct answer (the examiners were looking for,) take a reading of said barometer on the ground and take another on top of said, building and some how use the difference in air pressure readings to arrive at a height?
B Franklin

#### Solvay_1927

• Sr. Member
• Posts: 383
##### Re: Barometer
« Reply #3 on: 31/10/2005 21:27:29 »
It would appear so.

"Eagles may soar, but weasels don't get sucked into jet engines."

#### The Naked Scientists Forum

##### Re: Barometer
« Reply #3 on: 31/10/2005 21:27:29 »