A Bit of Physics Humour


Courtesy : Srinivas Rao, my IIMB Batchmate

Sir Ernest Rutherford, President of the Royal Academy, and recipient of the Nobel Prize in Physics, related the following story:

“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 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 hadn’t 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 his 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 [gravity] 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 tack, 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, “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 name of the student was…

Neils Bohr

The Nobel Prize winner in Physics 1922

Courtesy : Srinivas Rao, my IIMB Batchmate

Regards

Vijay Srinivasan
6th August 2008
Mumbai

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74 comments

    • Aeiluindae

      I’ve seen this story a couple of other places. Whether its true or not, It’s certainly entertaining, and makes the point that creativity of though is often more valuable than having the generally accepted answer.

    • cdmsr

      Speaking of morons: “This as fake…” is a moronic error. Since the ‘i’ key is some distance from the ‘a’ key, this is obviously not a typo. It is just a sour human being in such a rush to project his negativity into the world that he couldn’t take the time to proof his poison.

      Shameful. And sad.

      Also, apocryphal as it may be, the story is amusing and instructive.

      • asdf

        Having a go at someone because of a typo? That doesn’t prove they’re stupid. Just as looking up ‘apocryphal’ in the thesaurus doesn’t make you smart. Aeiluindae made a much more convincing and relevant point.

      • cdmsr

        asdf, you apparently lack the ability to comprehend simple writing — my comment addressed the typo hypothesis — but then you consider ‘apocryphal’ beyond an average vocabulary. Maybe you could search for some children’s sites so you want feel so outclassed and intimidated.

        Ans I wasn’t going after him for the typo: I was going after him for being an asshole. Are you related?

        I hope you check back since you chose not to receive comments, chicken shit.

      • cdmsr

        And the ‘s’ and ‘a’ are next to one another on the keyboard. Hence, a typo — not a spelling error. And, as I pointed out to another individual, I was not going after the typo but, rather, the a-hole.

        Do you have an actual point you would like to make? That comment has been up so long I barely remember posting it. And you are the first person that was sufficiently knobknocked to feel a need to point out an obvious TYPO. Guess that puts you in the a-hole category, too.

      • cdmsr

        Yeah, whatever. I didn’t exit the site to check the exact nature of the typo but the circumstance holds: side-by-side keys. So now you reveal that you are not only an asshole, but a pedantic asshole.

      • Somebody

        “… some children’s sites so you want feel so outclassed and intimidated.”

        Maybe you meant “won’t”, that way your sentence would make sense. And oh my, look at that, ‘a’ and ‘o’ are so far away from each other in the keyboard.. and what is that I see? An apostrophe? You must be a gigantic stupid idiot for making such a typo AND missing the apostrophe. Congratulations, you’ve made the biggest fail trying to point out a fail. (that I’ve seen today).

        (I know it’s old, but who cares, you are probably still a stupid idiot)

  1. THEMEDIA

    Several of the “other” answers do not follow the guidelines that clearly indicate “the answer should show some knowledge of physics.”

  2. Phylonyus

    but what if I went through and gathered the facts that showed that chemistry is derived from physics, biology from chemistry, and then neurology a reformed biology? Then the superintendent’s risk/reward management for receiving a barometer in return for answering the question is a physics problem, kinda.

  3. steve

    You posters are a pedantic bunch of nerds. It was a story about creative free thinking. The possibility of it’s falsehood in no way detracts from the validity of the message. Jeez.

  4. Travis

    True or not, it’s a great story in regards to free thinking. Anybody can be TAUGHT to think or act a certain way; yet very few individuals are able to construct such ideas on their own.

  5. Lex

    OK, so my 8-year-old son brought home a worksheet from class that listed several statements and asked the student to determine whether each was a fact or an opinion. One of them was, “This product has been rated No. 1 by X magazine.” My son had called that one opinion, which was not the answer the teacher was looking for. I asked him why he had labeled that one opinion. “Because, Daddy,” he said patiently, “the number was a fact, but it was really the magazine’s opinion.”

    I liked that approach so much I e-mailed his teacher about it.

    He did something similar one other time, with a reading worksheet containing a short piece in the form of a letter home from a girl at camp to her parents, telling them what she’d been doing. The question was, “What do you think was the writer’s purpose?” and my son had written, “To teach you to read better.” He said that the girl wasn’t the real author, the real author was the person who had created the worksheet, and THAT person’s purpose had been to help students read better.

    I’m not arguing my son is the next Neils Bohr. In fact, I foresee academic difficulty the next few years until he gets to a level where that kind of thinking is encouraged. But I am happy that when he gets a “wrong” answer, he sometimes has very good reasons for doing so.

  6. Vj (yeah even I cal myself as Vj)

    that was too good. whatever the facts of the story, it was funny and did throw some light on the way we teach our next generation. BTW ur topping stumble and now u will also be in the tweet world.

  7. J

    Funny that it requires ‘Niels Bohr’ to add meaning to the story, when it is a story about thinking outside of authoritative channels.

    The story was very funny, and informative. The negativity in the comments speaks more about the posters than the story.

    But why would this student only make sense in what he was saying if he was ‘Niels Bohr’? Truth is, we should all be tired of school teaching you what to think rather than how to think.

    J

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  11. Annie Delmont

    Thank you, Vijays, for this free mind lesson
    I am a physics teacher in France and I find it funny enough to wish showing it to my students
    So I would like to know more about it : where this story comes from, if you know about it…
    Regards
    Annie

    • Vijay Srinivasan

      Dear Ms Annie Delmont

      As I had mentioned in my blog post, the information came from my old college mate. I am sorry I do not have the bibliographical data on this matter. You might have to do your own research to find out !

      Thanks for reading my blog.

      BEST REGARDS

      VIJAY SRINIVASAN

    • GerbenB

      The conventional answer is:

      Ask for the name of the building, say it is named “Bellevue”.

      Define a measure of length: One bellevue equals the height of the building considered.

      Try to get it added to the SI (le Système international d’unités).

      Give the answer to your professor: The building is exactly one bellevue high.

  12. BAZA

    The conventional answer is to use the barometer to measure the pressure.
    A barometer it´s used to measure pressures so the teacher wanted to link the differences of pressures with the height of the building.
    If you consider that the building isn’t tall enough so that gravity acceleration changes significantly you can use the following equation: Pf-Pi= ro*g*(Xf-Xi), where Pf and Xf are the pressure on top off the building and it´s height and Pi and Xi are the pressure on ground level and the height of the ground, that we consider 0 meters, ro it´s the air´s density and g the gravity acceleration on Earth.
    Then you measure the pressure on the ground and on the top you the building and the only unknown in the equation is the height which is easily calculated.
    This method requires that the weather is calm and the atmospheric pressure remains constant so that the difference of pressure is only due to height and not to air streams or atmospheric conditions.
    If the building was big enough so that gravity changes significantly you would have to change g for mg=GmM/(x+Re) which the equation of universal gravitation. I´m not demonstrate this solution because it evolves integral and by now you must understand the method.

    BAZA, Portuguese Student of Physics

  13. BAZA

    I forget the square in (x+Re)^2.
    Anyway for more detail ask you teacher. He surely know the conventional way to do( his favourite way 😉 ).

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  15. chevy

    i´m teacher, and i try to encourage the free thnking on my students
    i like this so much that i don´t even care if it´s true or not, because the thing that matters is the lesson that this history gives to you

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