Bonus Question 2: "In various explosion scenes in movies, we often see this scenario: a chimney is falling down and, during the fall, it breaks into two pieces. Where will the break occur on the chimney?"
I know the answer to this question!
Wang Dazhuang raised his hand almost immediately after the three of them finished reading the question.
He raised his hand; he really raised his hand.
Zhou Mi looked at Wang Dazhuang, who had taken the initiative to speak, with a twitching expression, and could only nod to him.
"The fracture is in the middle!"
Wang Dazhuang spoke with a firm tone, as if he had already seen the answer.
"Why?" Zhou Mi asked.
"This question doesn't require an explanation of why, but I'm pretty sure the break is in the middle."
"Why?"
Since Zhou Mi asked "why" twice, Wang Dazhuang couldn't help but use a trick on her: "Do you know which animal loves to ask 'why' the most?"
In Wang Dazhuang's view, Zhou Mi, a top student, is all about doing practice problems. If she's not doing problems, she's working to earn money. This kind of routine is bound to be successful every time.
Even though Zhou Mi hadn't seen this joke before, her intelligence was enough to quickly analyze that it was definitely a cliché, and a very old one at that!
So, speechless, I replied, "I don't know."
"It's a pig!" Wang Dazhuang shouted excitedly.
"Oh," Zhou Mi replied calmly.
Hmm? This isn't following the expected approach. Shouldn't the correct answer be to ask "Why?"? Then everything would fall into place!
Frustrated, Wang Dazhuang couldn't help but ask, "Don't you want to know why?"
"In no mood."
"Why?"
"......"
Zhou Mi twitched her lips, looked at Wang Dazhuang with a resentful expression, then looked him up and down and nodded with approval.
Li Lechen burst out laughing and was clutching his stomach, barely able to stand up straight.
Trying to steal a chicken but losing the rice instead, failing to catch a fox but getting yourself into trouble—Wang Dazhuang certainly learned this lesson the hard way. When the Chinese exam requires these idioms, he'll definitely be able to use them.
Let's get back to the question.
Zhou Mi continued seriously, "This problem definitely won't break in the middle. It's a very complex mechanics problem, and it should involve angular velocity. However, we haven't learned about angular velocity yet, so maybe we can build a mathematical model and solve it using advanced calculus."
I probably didn't learn advanced mathematics either.
"How about we skip this question and do the math test first?" Li Lechen suggested. "The multiple-choice and fill-in-the-blank questions are faster."
"I've already done those questions, so it doesn't matter whether I do them again or not," Zhou Mi admitted.
It didn't matter to Zhou Mi whether she did those questions or not, but it did matter to Li Lechen; he was waiting to copy them.
Finished, Zhou Mi wasted no more time and immediately entered a series of problem-solving modes typical of top students, such as drawing diagrams, force analysis, and listing formulas.
However, this problem was indeed difficult. After three or four minutes of calculation, Zhou Mi ended up starting over. She even went so far as to look up formulas in a book.
Li Lechen began to get anxious.
"Is this question really that difficult?!" Li Lechen suddenly shouted.
[It's not difficult at all; this knowledge point is the 8,653,065th entry in "Ten Trillion Whys"]
It's just two-thirds of the way through, what a simple question!
Yes, two-thirds.
[Don't just give the answer, the host needs to explain.]
[It's quite simple. Before it broke, the entire chimney was clearly falling at the same angular velocity. Considering the top of the chimney, due to its own gravity, it should have fallen faster, but it was forcefully pulled back to the same angular velocity as the bottom of the chimney. This caused the chimney to eventually break. Calculations show that the break will occur at about 2/3 of the way down the chimney.]
This is what a force diagram looks like...
If we use angular velocity for calculation, we need to use the formula...
This problem can also be solved mathematically, without even needing to draw a free-body diagram, as long as...
In response to Li Lechen's sudden question, the viewers in the live stream immediately responded, not only giving the correct answer but also providing various detailed explanations.
Let's ignore the detailed explanations that are completely incomprehensible for now.
"It's just two-thirds, isn't it? Why is it so complicated?" Li Lechen quickly "plagiarized" the answer from the comments section, following up on his earlier statement.
"puff--"
This time it was Wang Dazhuang's turn to burst out laughing: "Yours is not even half of mine. Do you think two-thirds is more accurate? Then I'll guess three-fifths."
"It's two-thirds, I'm sure of it," Li Lechen said angrily after giving Wang Dazhuang a sharp look.
Zhou Mi had a good grasp of the fly problem from before, but with this chimney fracture problem, she couldn't figure out whether it was two-thirds or three-fifths unless she calculated it from beginning to end. It might even be one-half, or some complicated answer involving square roots.
Seeing that Zhou Mi also looked unconvinced, Wang Dazhuang became even more confident: "I have a theoretical basis for saying it broke at the halfway point, because the gravitational acceleration of any object on Earth is the same. When they fall together, the force they experience is the same, so it will naturally break in the middle. How did you guess that it broke at the two-thirds point?"
At first glance, Wang Dazhuang seems to be approaching the theoretical level of a top student.
Li Lechen was too lazy to bother anymore.
Actually, he couldn't pronounce the names of those complicated formulas, all the symbols and such. He only recognized addition, subtraction, multiplication, division, and Arabic numerals, and at most, he could add alpha and beta.
Since you can't read it aloud, just write it down.
So he quickly copied the design onto the manuscript.
You can't read it, and you can't understand it, but you can still copy it. This is an essential skill for academic underachievers.
"Oh, right!" Li Lechen suddenly stopped writing halfway and looked up at Zhou Mi.
Zhou Mi, who was engrossed in watching, was immediately bewildered, finally experiencing firsthand what it felt like to desire something you can't have.
Li Lechen sighed unhurriedly, "This question takes too much time. I'm afraid I won't have enough time. Otherwise, I'll do it when I get back and then give it to you. You can do the multiple-choice questions on the other test papers first and let us copy them."
"I'll finish the other questions tonight and take pictures of them for you. Oh no, you can just take my test paper and make copies," Zhou Mi said without hesitation. "You'd better finish this question quickly!"
"Well... alright then." Li Lechen shrugged, seemingly still reluctant. But in reality, he was overjoyed.
With the bargaining chip in hand, Li Lechen continued to meticulously copy the solutions from the comments, including four or five different ones. These solutions involved force analysis, calculations using angular velocity, and advanced mathematics. One solution even incorporated many professional formulas from engineering blasting. Ultimately, all the solutions pointed to two-thirds of the solution.
At this moment, Zhou Mi should have cherished the time and quickly finished the multiple-choice and fill-in-the-blank sections of the remaining test paper, but she was too surprised and was eager to learn about so many different solutions.
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