Page 22 - Analog Circuit Design Art, Science, and Personalities

Alexander Calandra

1. Barometers and Analog Design

Some time ago 1 received a call from a colleague, who asked if 1 would be the ref-
eree on the grading of an examination question. He was about to give a student a
zero for his answer to a physics question, while the student claimed he should
receive a perfect score and would if the system were not set up against the student.
The instructor and the student agreed to an impartial arbiter, and 1 was selected.
I went to my colleague’s office and read the examination question: “Show how it
is possible to determine the height of a tall building with the aid of a barometer.”
The student had answered: “Take the barometer to the top of the building, attach
a long rope to it, lower the barometer to the street, and then bring it up, measuring
the length of the rope. The length of the rope is the height of the building.”
I pointed out that the student really had a strong case for full credit since he had
really answered the question completely and correctly. On the other hand, if full
credit were given, it could well contribute to a high grade in his physics course. A
high grade is supposed to certify competence in physics, but the answer did not con-
firm this. I suggested that the student have another try at answering the question. I
was not surprised that my colleague agreed, but I was surprised that the student did.
I gave the student six minutes to answer the question with the warning that the
answer should show some knowledge of physics. At the end of five minutes, he had
not written anything. 1 asked if he wished to give up, but he said no. He had many
answers to this problem; he was just thinking of the best one. I excused myself for
interrupting him and asked him to please go on. In the next minute he dashed off his
answer which read:
“Take the barometer to the top of the building and lean over the edge of the roof.
Drop the barometer, timing its fall with a stopwatch. Then using the formula S =
0.5 ut2, calculate the height of the building.”
At this point, I asked my colleague if he would give up. He conceded. and gave
the student almost full crcdit.
In leaving my colleague’s office, 1 recalled that the student had said he had other
answers to thc problem, so I asked him what they were. “Oh, yes.” said the student.
“There are many ways of getting the height of a tall building with the aid of a
barometer. For example, you could take the barometer out on a sunny day and
measure the height of the barometer, the length of its shadow, and the length of the
shadow of the building, and by the use of simple proportion, determine the height
of the building.”
“Fine.” I said, “and the others?”
“Yes.” said the student. “There is a very basic measurement method you will
like. In this method, you take the barometer and begin to walk up the stairs. As you
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Rcprinted with permission of Teledyrie Components.

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