Physics Jokes
"Barometers and Analog Design" by Alexander Calandra.
Some time ago I received a call from a colleague, who asked if I would be the referee 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 I 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 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."
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 confirm 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 when 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. I 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*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. In 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. "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 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."
"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, to use the "scientific method," and to explore the deep inner logic of the subject in a pedantic way, as is often done in the new mathematics, rather than teaching him the structure of the subject. With this in mind, he decided to revive scholasticism as an academic lark to challenge the Sputnik-panicked classrooms of America.
THE SECRET OF ANTIGRAVITY...
If you drop a buttered piece of bread, it will fall on the
floor butter-side down. If a cat is dropped from a window
or other high and towering place, it will land on its feet.
But what if you attach a buttered piece of bread, butter-side
up to a cat's back and toss them both out the window?
Will the cat land on its feet? Or will the butter splat on
the ground?
Even if you are too lazy to do the experiment yourself you should be
able to deduce the obvious result. The laws of butterology demand
that the butter must hit the ground, and the equally strict laws of
feline aerodynamics demand that the cat can not smash its furry back.
If the combined construct were to land, nature would have no way to
resolve this paradox. Therefore it simply does not fall.
That's right you clever mortal (well, as clever as a mortal can get),
you have discovered the secret of antigravity! A buttered cat will,
when released, quickly move to a height where the forces of
cat-twisting and butter repulsion are in equilibrium. This equilibrium
point can be modified by scraping off some of the butter, providing
lift, or removing some of the cat's limbs, allowing descent.
Most of the civilized species of the Universe already use this
principle to drive their ships while within a planetary system. The
loud humming heard by most sighters of UFOs is, in fact, the purring of
several hundred tabbies.
The one obvious danger is, of course, if the cats manage to eat the
bread off their backs they will instantly plummet. Of course the cats
will land on their feet, but this usually doesn't do them much good,
since right after they make their graceful landing several tons of
red-hot starship and pissed off aliens crash on top of them.
And now a few words on solving the problem of creating a ship using the
aforementioned anti-gravity device.
One could power a ship by means of cats held in suspended animation (say,
about -190 degrees Celsius) with buttered bread strapped to their backs,
thus avoiding the possibility of collisions due to tempermental felines.
More importantly, how do you steer, once the cats are all held in stasis?
I offer a modest proposal:
We all know that wearing a white shirt at an Italian restaurant is a
guaranteed way to take a trip to the laudromat. Plaster the outside of
your ship with white shirts. Place four nozzles symmetrically around the
ship, which is, of course, saucer shaped. Fire tomato sauce out in
proportion to the directions you want to go. The ship, drawn by the
shirts, will automatically follow the sauce. If you use t-shirts, you
won't go as fast as you would by using, say, expensive dress shirts. This
does not work as well in deep gravity wells, since the tomato sauce (now
falling down a black hole, perhaps) will drag the ship with it, despite the
counter force of the anti-gravity cat/butter machine. Your only hope at
that point is to jettison enormous quantities of Tide. This will create
the well-known Gravitational Tidal Force.
An atom walks into a bar - very depressed.
The bartender asks him:
"What's wrong?"
"I lost my electron.."
Replies the atom.
"Are you sure?"
Asks the bartender.
"I'm positive."
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