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In 1590, Galileo Galilei did an experiment on the Leaning Tower of Pisa where "two iron balls hit the ground at the same time", and came to the conclusion that two iron balls of different weights fell at the same time, thus overturning Aristotle's theory that "the falling speed of an object is proportional to its weight", and correcting this erroneous conclusion that lasted for more than 1,900 years.

But this is unlikely, objects of different weights can only land at the same time under vacuum, and the law of free fall was proved when American astronaut David Scott tried to drop a feather and an iron hammer at the same height at the same height after landing on the moon, and found that they landed at the same time.

Even if Galileo did do this experiment, it was limited to the level of technology at the time, so it "seemed" to land at the same time. Regarding the free fall experiment, Galileo did a lot of experiments, he stood on top of the leaning tower and made objects of different materials fall from the top of the tower, and measured the difference in the time of falling.

It was found that all kinds of objects landed at the same time, in no particular order. In other words, the falling motion is not related to the specific characteristics of the object. Regardless of whether the ball is wooden or iron, if it starts falling from the tower at the same time, they will reach the ground at the same time.

Through repeated experiments, Galileo believed that the free fall velocity of light and heavy objects is the same, that is, the magnitude of gravitational acceleration is the same, regardless of air resistance.

Extended Materials. The formula about acceleration due to gravity can be deduced using Newton's law of universal gravitation.

When an object above the earth takes the center of the earth as the reference point to describe its motion, it is moving in a uniform circle around the earth, and the resultant external force experienced by the object in the direction of the line with the center of the earth is a centripetal force pointing to the center of the earth, and this centripetal force is provided by the gravitational force between the object and the earth, i.e. f direction = f million, according to Newton's second law formula followed by the centripetal force: f = mg and the formula of the law of gravitation

Answer]: A The knowledge points examined in this question are the practical standards for testing the true Tandan. The universal and immediate reality of practice determines that it is the only criterion for testing truth.

But universality is both a practical and a theoretical characteristic. Direct reality is unique to the circle made by practice, and it is also the point at which practice is superior to theory, and it is the main basis for practice as the criterion for testing truth. So the correct answer to this question is A.

Options c and d, although also features of practice, have nothing to do with the topic.

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Problem description: It is said that Galileo did a famous experiment in the Leaning Tower of Pisa in which two iron balls of different weights fell at the same time, but in Hawking's "A Brief History of Time", this statement was questioned, and it was said that Galileo did not do this experiment, but only made a similar experiment, that is, a large and a small mass, two iron balls with different masses sliding freely from a smooth inclined plane.

Analysis: Galileo did not do this experiment.

Galileo only said that if there were two stones, one large and one small, falling from the top of the tower together, then according to the experience of the people of that time, it must have been the heavier (i.e., the big stone) that landed first. So if you tie these two stones together and let them fall, according to this experience, if two stones are heavier than one stone, they will fall faster, but the other way around: the big stones are supposed to fall faster than the small stones, and if they are tied together, they will fall slower due to the influence of the small stones.

In this way, according to the experience of the predecessors [the heavier physical fall is faster], the falling speed of the two stones is different. So it turns out that [the heavier physical falls faster] is a paradox.

But he really didn't do the experiment.

At the time, it was thought that heavier objects would fall faster and that their acceleration would be proportional to their mass, but this was not the case.

Galileo discovered that gravitational acceleration is certain and has nothing to do with the mass of the object, so he did an experiment to throw two balls with a mass difference of ten times from the Leaning Tower of Pisa at the same time, according to the theory at that time, the speed of the big ball should be ten times that of the small ball, and landed in advance, but the two balls landed at the same time, Galileo used this experiment to change people's misconceptions. 2. At that time, it was believed that the heavier the object falling at a faster rate, and its acceleration was proportional to its mass, but this was not the case.

Galileo discovered that the acceleration of gravity is certain and has nothing to do with the mass of the object, so he did an experiment and threw two balls with a difference of ten times the mass from the Leaning Tower of Pisa at the same time. That's why I did the experiment. 2. At that time, it was believed that the heavier the object, the faster it falls, and its acceleration is proportional to its mass, but this is not the case.

Galileo discovered that gravitational acceleration is certain and has nothing to do with the mass of the object, so he did an experiment and threw two balls with a mass difference of ten times from the Leaning Tower of Pisa at the same time. 2. At that time, it was believed that the heavier the object, the faster it falls, and its acceleration is proportional to its mass, but this is not the case.

Galileo discovered that the acceleration of gravity is certain and has nothing to do with the mass of the object, so he did an experiment and threw two balls with a difference of ten times the mass from the Leaning Tower of Pisa at the same time. 0,

It has been proved that objects of different weights and weights will hit the ground at the same time when they fall from the same height with the same acceleration, thus overturning Aristotle's erroneous assertion. This is what Galileo proved and now known as the law of free fall.

The acceleration due to gravity is both g m g

The Leaning Tower of Pisa Experiment "provides a vivid illustration of the fact that practice is the only criterion for testing truth, as an example of natural science."

Galileo Galileo Pisa's Leaning Tower Iron Ball Test), which actually examines non-free-fall motion.

The same postcard is subject to the same gravity, so the main thing that affects the postcard is the air resistance, the vertical fall is subject to small resistance, and the horizontal fall is large, so the vertical fall falls first, and the postcard is behind, if it is all iron balls, the vertical fall is subject to little resistance, and at the same time land.

To prove this point, one day in 1589, Galileo, a young mathematician at the University of Pisa, at the age of 25, arrived at the Leaning Tower of Pisa with his debaters and many others. Galileo climbed to the top of the tower and dropped a 100-pound and a one-pound iron ball at the same time. In full view of everyone, the two iron balls unexpectedly fell to the ground almost parallel to each other.

In the face of this ruthless experiment, the people present were all stunned and at a loss.

This beautiful story, known in the scientific community as the "Leaning Tower of Pisa Experiment", proved that objects of different weights and weights would hit the ground at the same time when they fell from the same height with the same acceleration, thus overturning Aristotle's erroneous thesis. This is what Galileo proved and now known as the law of free fall. The Leaning Tower of Pisa Experiment "provides a vivid illustration of the fact that practice is the only criterion for testing truth, as an example of natural science."

In 1590, at the age of 26, Galileo Galilei conducted a falling experiment on the Leaning Tower of Pisa. He specially invited some university professors to come**, and many people also came to watch after hearing the news.

I saw Galileo carrying two iron balls, one weighing a kilogram (100 pounds) and the other weighing a kilogram (1 pound), and he climbed to the top of the tower like a warrior on a march. When he announced to the people that the two iron balls, one large and one small, would fall at the same time and would hit the ground at the same time, the people under the tower began to talk as if they were boiling a pot: "Is Aristotle really wrong?"

It's absolutely impossible! "This guy must be crazy! ......

Galileo heard these comments and ridicules, and he calmly said loudly and confidently: "Gentlemen, don't be too busy jumping to conclusions, let the facts speak for themselves!" After speaking, he stretched out his hands and made the two iron balls fall from the tower at the same time, only to see them fall in parallel, falling faster and faster, and finally "snapping" and landing at the same time.

Faced with the irrefutable facts of the experiment, those Aristotle's faithful believers were dumbfounded and overwhelmed, and had no choice but to walk away in disgrace. The Leaning Tower of Pisa experiment not only overthrew the erroneous doctrines of the ancient authorities and ended its nearly 2,000-year domination of the academic world, but also ushered in a new era of modern scientific experimentation.

Today, anyone who knows a little about physics knows that objects of different weights and sizes can fall freely from the same height at the same time, and if there is no air resistance, they must hit the ground at the same time. However, until the 16th century, people believed in the doctrine of Aristotle, the authority of ancient Greece. He thinks:

The speed of the object falling is determined by the weight of the object, the heavier the object, the faster it falls, for example, a 10 kg object falls, which is 9 times faster than a 1 kg object. At that time, it was written in textbooks and taught by university professors.

Still, there is a suspicion that Galileo is the most famous of them. After careful consideration and repeated experiments, he confirmed that the doctrine that "the heavier the object, the faster it falls" is wrong. You know, in the eyes of Europeans at that time, apart from God, only Aristotle was absolutely right.

Whoever dares to oppose him and say that he is not is a great rebellion. The brave Galileo insisted on the truth and decided to experiment in public, openly challenging the ancient authorities.

A young friend may say that if Galileo put down a paper ball and an iron ball on the leaning tower at the same time, then the iron ball must have landed first. That's true. While the paper ball was still floating in the air, the iron ball had hit the ground. Is this true of Aristotle's doctrine?

It is likely that Aristotle drew his conclusions from such phenomena, but he was deluded by illusions. In fact, when an object falls through the air, it is subject to air resistance. The paper ball is light, and the influence of air resistance is large, which cannot be ignored; The iron ball is heavy, and the effect of air resistance is small and negligible.

If the paper ball and the iron ball fall at the same time in a vacuum, the influence of air resistance is excluded, and they will definitely fall to the ground at the same time.

Did Galileo really do a freefall experiment on the Leaning Tower of Pisa?

Because he wanted to confirm Aristotle's words.