Barometer - Measuring height of a very tall building

The teacher asks a student how he would measure the height of a very tall building using a barometer,
evidently expecting to hear about reduced air pressure being proportionate to the elevation....
The student says: Tie the Barometer to a long string till the barometer touches the ground, measure
the length of the string!
However, what follows is much more interesting;
This highly original answer so incensed the examiner that the student was failed. The student went in
appeal on the ground that his answer was indisputably correct, and the University appointed an independent
commission to decide the case. The commission judged that the answer was indeed correct, but did not
display any noticeable knowledge pf 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 minimum familiarity with the basic principles of physics.
For five minutes the student sat in silence, forehead creased in deep thought. The commission reminded
him that time was running out, to which the student replied that he had several extremely relevant answers,
but could not 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 want 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 square root (1/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....



Karippara Sunil said...

we can use this in todays cluster

ict4tamil said...

Please collect & upload the needed resources, essays and physics poems etc... for 8, 9 and 10 th students. Please update the blog atleast twice in a week.