Saw this on YouTube, just wanted to share
DETERMINE THE HEIGHT OF A TALL BUILDING WITH THE AID OF A BAROMETER
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 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.
Some interesting facts about the Milky Way galaxy
1. A 250-Million-Year Orbit
On Earth, a year is determined by the length of time it takes the planet to orbit the Sun. Every 365 days, we’re right back where we started, generally speaking. It makes sense then that our entire solar system is similarly orbiting the black hole at the center of the Milky Way. It just takes a little longer, to the tune of 250 million years for each rotation. In other words, we’ve made about a quarter of a single orbit since the dinosaurs died.
Descriptions of the solar system rarely mention that it’s spinning through space just like everything else. We’re actually traveling at about 792,000 kilometers (483,000 mi) per hour relative to the center of the Milky Way. To put that into a more easily relatable example, that speed would take you around the Earth in just over three minutes. Each time the Sun makes it all the way around the Milky Way, it’s known as the galactic year, or cosmic year. It’s estimated that there have been only 18 galactic years in the history of the Sun.
2.Twin Galaxies
While the Milky Way might be unique in many ways, it’s safe to say it’s not exactly rare. We already mentioned that spiral galaxies are one of the most common types in the universe; add to that the fact that there are around 170 billion visible galaxies, and it wouldn’t be a stretch to imagine that there could be a few galaxies out there very similar to our own.
But what about one that’s almost an exact replica of ours? In 2012, astronomers discovered a galaxy that shares a likeness with everything we know about the Milky Way. It even has two small satellite galaxies orbiting it, perfectly corresponding to our own Magellanic Clouds. And that’s rare—only 3 percent of spiral galaxies have companion galaxies like that, and they don’t last long. The Magellanic Clouds will probably dissipate in a couple billion years, a leisurely afternoon on the cosmic time scale. To find another barred spiral with a supermassive black hole center that also has two satellite galaxies the same size as our own is highly unlikely, to say the least.
The galaxy is named NGC 1073, and it’s so similar that astronomers are actually using it to learn more about our own galaxy. Since we’re too deeply embedded for any kind of perspective on the Milky Way, NGC 1073 gives us that top-down view that we’ve always needed to fully study our own neighborhood.
3.Cosmic Warping
Although the Milky Way is a spiral by definition, that’s not an entirely accurate way to think about it—there’s actually a bulge at the center of the galaxy, so the whole thing sort of looks like a pancake with a pile of whipped cream on each side. The warped section is the result of hydrogen gas molecules stretching away from the two-dimensional plane of the spiral.
For years, astronomers were mystified by the seemingly inexplicable warping. By all logic, the gas should be pulled toward the disk, not away from it. The more they studied it, the deeper the mystery ran—because the molecules in the warp are not only pulling away, they’re vibrating at a frequency of their own.
So what’s causing it? As far as we can tell, dark matter and a duo of small galaxies known as the Magellanic Clouds. When they’re put together, the Magellanic Clouds have about 2 percent of the Milky Way’s mass—not enough to affect it much. But when dark matter moves through the Clouds, it creates ripples that apparently affect their gravitational pull on the Milky Way. This strengthens the pull and entices the hydrogen away from the center of our galaxy.
And it gets even weirder. The Magellanic Clouds orbit the Milky Way, so as they make each revolution, the spiral arms of the Milky Way flap in response to their presence like a flag waving in the wind.
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