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Subject:So I Remember This
Time:06:13 pm
I don't even know if this is true or not, but it's a very good story, and I want to remember it; So I'm posting it here, I hope you enjoy:

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.

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kirkjerk
Link:(Link)
Time:2007-10-30 12:03 am (UTC)
Ok, at the risk of spoiling a lovely story:

First off, I love this chestnut of a story. It's a terrific study in lateral thinking.

I think the "Neils Bohr" bit is a retcon; previously I saw it end on the "I will give you this fine barometer" line, which is a bit punchier.

But now I'm musing on the ending. I've been thinking about "bubble tests" lately, the SAT etc. I did very well on those, which was a lovely ego boost and a boon for college admission. I'm totally willing to believe there's only a so-so correlation between these tests and "smarts", but I'm unwilling to buy into the idea that "the only thing they test is how well you take tests". My current favorite (untested, but anecdotally supported) theory: there is a surprisingly strong correlation between reading speed and test scores. A number of people who I think of as clever, but they did poorly on the tests have said they aren't such fast readers. (Not sure if it's correlation or causation, but there are some arguments for the latter including being more able to check your work.)

But anyway, that's a tangent. My point was this: when taking a test it's good to be meta- about it. Often a thought about WHY they're asking a particular question, or providing those possible answers, is extremely useful. And I used to be a fighter; if I saw 2 choices that met the question as it was asked and got the right one based on a reading of the metaquestion, I would FIGHT for other kids who got the other "correct but not the right" answer, just because of my sense of justice and fair play.

So, I think asking a question with an "obvious right" answer isn't so bad. I would say that Bohr's other solutions all rely on having other props (a long rope, a stopwatch, a sunny day and a ruler, chalk and idiosyncratically architected stairs, string, rope AND a stopwatch, or a friendly and unusually knowledgeable superintendent.) Plus, several of them would probably cost you the barometer. I think the "correct" answer only requires the barometer and some knowledge. And roof access. But you get to keep the barometer.
(Reply) (Thread)


mkb_technologie
Link:(Link)
Time:2007-10-30 02:07 am (UTC)
niels bohr, japh
(Reply) (Thread)


thewallflower00
Link:(Link)
Time:2007-10-30 01:22 pm (UTC)
This is lifted from "Chicken Soup for the College Soul". It did not include Niels Bohr.
(Reply) (Thread)


kirkjerk
Link:(Link)
Time:2007-10-30 02:01 pm (UTC)
Hmm, Googling a bit, this seems to be a cite from 1964: http://138.100.110.21/ot1/the%20barometer%20story.htm - its been kicking around for a while, at one point was used to argue against "the new math".

Fun story though, no matter how long or spotty its pedigree.
(Reply) (Parent) (Thread)

screwjaw
Link:(Link)
Time:2007-10-30 03:44 pm (UTC)
Apparently, snopes can't prove or disprove the story or the role that Niels Bohr takes in it.

http://www.snopes.com/college/exam/barometer.asp

Re: the "how to think" and "rote" issues of the testing and such, I waver between the two views. On the one hand, following rote methods can help discipline the mind and develop self-control. The good counter argument, however, is that inductive thinking is important for innovation and dealing with situations that the rote thinking doesn't address. In the end, I have to argue for a balance between the two since both sides of the issue have their virtues.
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