Reshaping life starting from the Junior Class of HKUST

Chapter 289 Huang Minghai's Amazing Performance
"Old Zhang, why are you so impatient? They must not let them think about it. If it is easy, they will look down on the genius of your class 1!" Qian Feng rarely had the opportunity to tease Zhang Detong.

"Hmph!" Zhang Detong didn't bother to talk to him.

After a while, after the people in class 2 discussed it, Xu Dong went up to write the questions directly.

"Hey. Xu Dong, what subject is it? Why don't you reveal it first, and we can ask people to do it directly." Wang Chao said carelessly from below.

Xu Dong turned his head to look at Wang Chao, and said with a smile: "Don't pretend to be a wolf with a big tail, we don't bully others, this question is about mathematics. Your young master Wang is usually awesome, why don't you come up directly. "

"Hey! That's fine too! Since it's mathematics, it's okay?" After speaking, he stood up and greeted the people in his class: "Brothers and sisters, how about leaving this game to Master Wang? Canteen at noon please? "

Before the students around could speak, Zhang Detong's scolding sounded first: "Wang Chao, talk to me! Do you want me to call you Lord Wang too! Treating guests to the cafeteria at noon? I'm going to lose today, so I'll let you No food for three days."

Wang Chao was scolded by Lao Zhang, and immediately sat down obediently like an eggplant beaten by frost.

"Who told you to sit down? Go up and do the questions for me. Is it possible that you still have to call you Wang Ye? Can you go up?" Lao Zhang said bitterly: "If you are a man, you have to do what you say. To. In case someone loses and has an excuse."

After speaking, he squinted at Qian Feng.

"Hey! Mr. Zhang, just watch it." Wang Chao was so excited that he almost shouted out.

Everyone below suppressed their laughter, Zhang Detong's face was livid.You can't give Wang Chao a little bit of color, this is the owner of the little color dyeing workshop.

When Wang Chao came to the podium, Xu Dong had already written the inscription on the whiteboard:

Suppose the function y(x)(x≥0) is second-order derivable, and y'(x)>0, y(0)=1. Pass any point P(x, y) on the curve y=y(x) for The tangent to the curve and the perpendicular to the x-axis——.

两直线与x轴所围成的三角形的面积记为S1，区间[0，x]上以y=y(x)为曲边的曲边梯形面积记为S2，并设2S1-S2恒为1。

Find the equation of this curve y=y(x).
Wang Chao took the black pen and said with a smile: "That's it? Your level of questioning is too low. After discussing for so long, you came up with something like this? Check it out!"

After speaking, I started to write without thinking:
Suppose: the tangent equation of the curve y=y(x) at the point P(x, y) is

Yy=y'(Xx),

Its intersection with the x-axis is (xy/y', 0) -
According to the known condition 2S1-S2=1, there is
y2/y' - y(t) dt=1,

Substituting y(0)=1, there is y'(0)=1.
Derivate x on both sides of the equation and simplify to yy''=y'2,
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Therefore, the equation to obtain the curve is y=ex.
After finishing writing, he turned around and threw the pen on the podium.Domineeringly said: "Is this the difficulty? I can solve it in my freshman year of high school. Do you have sincerity in Class 2? Look down on us?"

"Cut!" There were boos from below.

Wang Chao would be bragging if he said he could solve this problem in the first year of high school.

Wu Zhe smiled from below, this kid's math skills are really good.Gently touched Huang Minghai who was beside him and said, "How many people in the class do you think can solve this problem?"

Huang Minghai frowned and thought for a while, "Don't look at what Wang Chao said so easily, I guess there are no more than ten people in the class who can solve this problem. I guess there are no more than three people who can do it as fast as Wang Chao. Our class is better than class 2, and there are those who are very good in various subjects. In fact, this method of competition, class 2 will suffer a lot."

Wu Zhe nodded, every subject has a gold medal winner in the competition.

Let alone Class 2 today, as long as students from the same class come from across the country, the rules of the competition still apply.Then no one can get cheap from this group of people.

"Old Qian, or you can let people go up first. We can also tell you the type of question." Seeing that Wang Chao easily solved the problem, Zhang Detong immediately said to Qian Feng.

"Hey! Don't say that you don't know how much your class has gained by this rule? Children compete, what do you think you are an adult participating in?"

Good guy, who was complacent when he first came in?This looks wrong.Is it just the little guy's competition?Zhang Detong was speechless to Qian Feng, you scoundrel is about to catch up with Wang Chao.

It's class 1's turn to come up with a question, this time it's physics plus math:

A certain detection instrument is sunk from the ship into the sea. According to the detection requirements, it is necessary to determine the functional relationship between the instrument’s sinking depth y (calculated from sea level) and the sinking velocity v. Suppose the instrument is under the action of gravity, from the sea The plane sinks vertically from rest, and is also affected by resistance and buoyancy during the sinking process. Assuming the mass of the instrument is m, the volume is B, and the specific gravity of seawater is ρ, the resistance suffered by the instrument is proportional to the sinking speed, and the proportional coefficient is k(k>0). Try to establish the differential equation satisfied by y and v, and find the functional relationship y= y(v).
Fortunately, there are still a few great masters in class 2. After bumps and bumps, the answer is finally calculated: y=-m/k vm(mg-Bρ)/k2 ln(mg-Bρ-kv)/(mg-Bρ ).
Class 2's counterattack was faster, and it was directly a question for comprehensive subjects.If a single one can't handle you, then don't think about it for everyone.

It is said that there are five questions, but except for the first question, which takes a little less time, the following questions take more time than one question.This competition started in the morning.It was already afternoon when the last question came.In the middle of the lunch, they take turns to go out to eat, and of course some people ask people to bring meals.

Fortunately, the first four questions were all passed, and Class 2 was poor in answering speed.This is also something that can't be helped, this kind of competition is actually more powerful than the competitive players of Class 1.

For the last question, class 1 comes out first, and the questions given are very simple:
A uniform cylinder rolls down from an inclined plane (without slipping). It has a mass M and a radius R. Find its kinetic energy when the angular velocity is w.

Wu Zhe was a little startled, which ghost came up with this question.It looks very simple, but if you are not careful, you will step on a trap.

"Who made this question? Is it too bad?" Wu Zhe couldn't help but quietly asked Huang Minghai next to him.

"Uh! Is it damaged? Are you okay?" Huang Minghai hesitated.

"Could it be you?" Wu Zhe asked suspiciously.

"Hey, you can just go to the theater!" Huang Minghai vaguely moved the subject.

Why did Wu Zhe say that the question was cunning, because the question looked simple, and after answering it, it was too late to find the mistake.

果然上去的人直接用的是：E=1/2[I(w^2)]+1/2m[(rw)^2]，滚动动能加平动动能，以接触点为圆心瞬间做圆周运动。

Seeing that he finished writing, Wu Zhe patted his forehead, and Class 2 was over.

Huang Minghai's hand is really sinister, it looks simple, but there is a logical error in it.This needs to regard the cylinder as a mass point and at the same time regard it as a collection of multiple mass points.

"Hahaha, Xu Dong, you are going to bow to us! This question is wrong." Wang Chao shouted happily.

At this time, people from class 2 also responded.When the people in class 1 explained it, they knew what was wrong.But it's useless to be annoyed.

"Wang Chao, don't rush to celebrate. Do we have another chance to come up with a question?" Xu Dong also calmed down quickly, and hurriedly pulled people together to think about it.

"Old Zhang, these little bastards seem to have a bet?" Qian Feng asked a little nervously.

"It's good to have a bet! As long as it's not gambling, some small bets can still promote feelings!" This time it was Lao Zhang's turn to be proud.The advantage is in hand, the most draw.If he can win, he can use it to embarrass his old money from time to time this semester. Isn't this more comfortable than drinking?

"It's not good to have a bet! Why don't you forget it? By the way, aren't we talking about their ideological problems today? Those boys' inspections haven't been written yet. You see, stop the competition first, and do it next time. How about leaving it in suspense?" Qian Feng pretended to suddenly remember that there was still business to do.

Zhang Detong gave him a sideways look, you are thinking about farts.Where did the elation go when you first came in and heard that your class had won a game first?If you want to lose now, you quit first?I have to close the door for you!

Qian Feng looked at Lao Zhang's posture, and if there is no decision today, won't he give up?Now we can only see if Xu Dong and his gang can help him live up to his expectations?
Class 2 just discussed the topic and discussed it for more than an hour.They can't help but be careful, this question should not be difficult for the meeting of Class 1. People who meet with Class 1 in that week have to make a detour, and no one wants to bow to others in public.

It was Xu Dong who went up and wrote the title:

The operating mass of the spacecraft on the landing preparation orbit is 2.4t, and the main reduction engine installed in the lower part can generate an adjustable thrust from 1500N to 7500N, and its specific impulse (that is, the thrust generated by a unit mass of propellant) is 2940m/s , which can meet the control requirements of adjusting speed.Attitude adjustment engines are installed around it. After the thrust direction of the main reduction engine is given, various attitude adjustment controls can be realized automatically through the pulse combination of multiple engines.The planned landing point of the spacecraft is 19.51W, 44.12N, at an altitude of -2641m.

In the case of high-speed flight, to ensure accurate soft landing in the predetermined area of ​​the moon, the key issue is the design of landing orbit and control strategy.The basic requirements for the design of its landing orbit: the landing preparation orbit is an elliptical orbit of 15km at the perilunary point and 100km at the apolunar point; the landing orbit is from the perilunar point to the landing point, and the soft landing process is divided into six stages. The state of each stage at key points; minimize fuel consumption during a soft landing.

Requirements: (1) Determine the positions of the perilunary point and the apolunar point of the landing preparation orbit, as well as the magnitude and direction of the corresponding velocity of the spacecraft.

(2) Determine the landing orbit of the spacecraft and the optimal control strategy in the 6 stages.

When Xu Dong finished writing, not only everyone in class 1 was stunned, but also Zhang Detong, Qian Feng and Wu Zhe were dumbfounded.In order not to lose, I don't even want to lose face.Wu Zhe couldn't think of anyone in the class who could solve this problem within an hour.

This is totally cheating.

"Xu Dong, are you going too far?" Huang Minghai, who is the best in physics, stood up and said.

"Hey, let's just say if you can solve it? We have a problem. Although it's a bit difficult, don't pick and choose."

Class 2 is not afraid of boiling water. If the question is difficult, it is easy to explain, but if it loses, it is admitted that it is not as good as class 1.

"Fart, is that a bit difficult for you guys? Feel your conscience and ask yourself, which one of you has the ability to solve it within an hour?" Huang Minghai refused to accept.

"Don't talk so much? Can you do it? If not, then we'll be considered a tie!" Someone from Class 2 shouted.

"Get out, the time hasn't come yet?" Class 1 refused to give up just like that, they were all burying their heads in the calculation.

"Old Qian, is this the student you teach? Did you learn to cheat and play tricks? I learned it from you?" Lao Zhang has something to say at this meeting.

Qian Feng's face was also flushed, and he cursed in a low voice: "I'll deal with them later."

Wu Zhe said softly at the bottom: "You divide the labor and cooperate, don't finish the questions alone, if one person completes the link, is it possible?"

Huang Minhai understood in seconds, and immediately shouted loudly: "The spacecraft landing preparation orbit equation, I will solve the corresponding speed of the far moon point and the near moon point."

Wang Chao immediately interjected: "Boss, you don't need to calculate, you will coordinate the parameters we need to calculate and use. Leave what you just said to me."

"Okay!" As soon as Wang Chao said this, Huang Minghai knew that Wang Chao was afraid that other people would not have the idea to solve the problem. It was the best choice for him to be the coordinator. He didn't procrastinate at all, he was very straightforward?
After thinking for a while, he continued to speak loudly: "The landing orbit and the landing coordinates are calculated together, who will come?"

"Leave it to me!" Shen Zhiwen said quickly beside him.

"The position of the perilunar point relative to the lunar center."

"I'm coming!" The relay started from behind.
-
"Coordinates of the far moon point"

"mine!"

"Kinetic equations and guidance laws for the various phases of a soft landing."

"mine!"
-
"Continuous Safe Zone Computation"

"mine!"
-
Almost everyone in class 1 was assigned the task.Huang Minghai didn't sit in his seat anymore, and quickly came to the blackboard in front of him and began to draw a form, dismantling each small goal into numbers, and filling in the grid above.

After doing this, he started to use a map to make the whole thinking process clearer, so that the people below can know what purpose their calculations are for.

Wu Zhe looked sideways, he was also very surprised by Huang Minghai's high level in aerospace.There is also the kind of straightforwardness and calmness.No wonder he was able to achieve the position of deputy chief engineer later.

"Boss, the relative calculation of the far-moon point and near-moon point has been quickly completed." Wang Chao was the first to report.

"Okay, later you will help others to check the calculations. You can't make mistakes. We will do it once this time." After speaking, he ticked Wang Chao's number in the task column on the form.

"Report, the coordinates of the far moon point are confirmed!"
-
"Report, the safe area has been calculated!"
-
"Report, the landing angle of the spacecraft is determined."
-
With the sound of one report after another, more and more numbers in the chart are ticked.

Finally, the last data calculation is completed.Huang Minghai looked at the time, and there were 3 minutes left to complete an hour.Immediately got up and gathered all the data.Start writing on the whiteboard.

"Huang Minghai, don't write anymore! We admit defeat! Congratulations!" Xu Dong stood up, losing, but he was convinced.

Wu Zhe stood up without speaking.Just "crack! Crack! Crack!" applauded, and then everyone stood up, clapping for Huang Minghai and himself.

The pride in Zhang Detong's eyes could not be hidden.Staring at the students in his class, their eyes are a little rosy.Just now when everyone united and cooperated, he was really stunned, and his whole body was like being electrified.Excitement, pride, relief, all kinds of emotions.

After the applause stopped, Zhang Detong shouted loudly: "We won! I am proud of you!"

The people in Class 1 cheered again.

It was already dark outside, and Wang Chao shouted loudly: "Dinner, let's have dinner together. I, Young Master Wang, treat you!"

Zhang Detong and Qian Feng didn't stop them and told everyone to go back.

After everyone left, Zhang Detong said, "Old Qian, are you convinced?"

Qian Feng sighed and said: "Submit! Huang Minghai is a great general!"

"Hahaha! Let's go, I'll buy you a drink!" Zhang Detong laughed heartily.

(End of this chapter)