Some time ago I received a call from a colleague. He was about
to give a student a zero for his answer to a physics question,
while the student claimed a perfect score.
The instructor and the student agreed to an impartial arbiter,
and I was selected.I 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 it 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."
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 and to
certify competence in physics, but the answer did not
confirm this.
I suggested that the student have another try. 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.
I asked if he wished to give up, but he said 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 x=0.5*a*t^^2,
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 credit. While
leaving my colleague's office, I recalled that the student
had said that he had other answers to the problem,so I
asked him what they were. "Well," 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 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 climb the stairs, you mark off the
length of the barometer along the wall. You then count
the number of marks, and this will give you the height
of the building in barometer units."
"A very direct method."
"Of course. If you want a more sophisticated method, you
can tie the barometer to the end of a string, swing it as
a pendulum, and determine the value of g at the street
level and at the top of the building. From the
difference between the two values of g, the height of
the building,in principle, can be calculated."
"On this same tact, you could take the barometer to the
top of the building,attach a long rope to it, lower it
to just above the street, and then swing it as a pendulum.
You could then calculate the height of the building by the
period of the precession".
"Finally," he concluded, "there are many other ways of
solving the problem.Probably the best," he said, "is to
take the barometer to the basement and knock on the
superintendent's door. When the superintendent answers,
you speak to him as follows: 'Mr. Superintendent,
here is a fine barometer. If you will tell me the height
of the building, I will give you this barometer."
At this point, I asked the student if he really did
not know the conventional answer to this question. He
admitted that he did, but said that he was fed up with
high school and college instructors trying to teach
him how to think. The student was Neils Bohr.
So I Remember This

Dirk Gently coming to the BBC!
http://www.bleedingcool.com/2010/08/25/bbcofficiallyannouncesdirkgentlytvshow/

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