"First establish a rectangular coordinate system in space, and then calculate the position of the center of gravity of the teacup according to the formula for the center of gravity."
For Xu You, who is also concerned with mathematics, such an operation is too basic.
Within a minute, Xu You found out the coordinates of the center of gravity of the teacup in this coordinate system.
"Just make the center of gravity of the teacup the closest to the stool."
In three minutes, Xu You finished the first question.
The second question involves the force analysis of three-dimensional objects.
Xu You quickly determined the cut plane and transformed it into plane force.
And according to the trigonometric function relationship, moment balance and other conditions, formulas are listed.
"Combine the 7th, 10th, and 11th formulas, and you can find the change in the final force."
In less than ten minutes, Xu You completed the entire process of the first question.
Based on the 3-hour test time, the time left for each question is about 20 minutes.
Xu You's speed gave this exam a good start.
This is the key to the difficulty of the rematch.
Many topics may be achievable if candidates are given enough time.
But the difficulty is to be able to complete the answer within the allotted time.
When Xu You finished the first question, some students had just started to build departments, and they didn't even know how to find the height of the center of gravity.
This has a lot to do with their lack of solid mathematical knowledge.
Originally, it was not easy to have time to prepare for a subject competition while studying in normal high school.
There are not many students who can prepare well for both competitions at the same time like Xu You.
The second question is a relatively simple geometric optics question.
Of course, it was for Xu You.
It can be done with equal optical path length, which is a relatively routine problem.
Questions 3 and 4 are not too difficult, but the amount of calculation is slightly larger. Xu You didn't spend more than 20 minutes on each question.
The five questions and six questions obviously started to become longer. If you don't look carefully, there is a sense of both ipho and apho.
For example, the fifth question has the concept of laser refrigeration. Generally, only ipho and apho can ask questions like this.
Of course, if you read the question carefully, you will find it.
Laser cooling is only briefly mentioned in it, and the main investigation is the Doppler effect of light and resonance absorption.
After finishing the first six questions, Xu You looked at the time, and there was still more than an hour left.
This speed is even faster than Xu You's plan.
Xu You can be given enough time to attack the last two big questions.
The last two big questions are often the hardest two.
The other students, hurry up, and have already done the fifth question.
Slow, just started answering the third question.
Also, some skipped parts are not included.
Of course, there are still many students in the semi-finals who have been completely defeated by the questions and choose to quit the exam early.
They can only admit with regret that competition is not their battlefield.
They are just a little better in physics in ordinary high school, so let's go back and prepare for the college entrance examination with peace of mind.
"The seventh question is actually not too difficult."
A dynamics problem mainly examines the force analysis of rigid bodies.
The difficulty of thinking is medium, and it can only be said that the amount of calculation is slightly larger.
For three small questions, Xu You listed more than twenty formulas back and forth.
Although Wu Jing can use a calculator, but for some relatively simple calculations, Xu You directly calculated them by himself.
This is also an experience that Xu You summed up.
Unless it is a particularly large number or a particularly difficult equation, writing calculations may be more convenient than calculators.
In twenty-five minutes, Xu You completed the entire process of the seventh question.
There are more than forty minutes left to solve the last question, which can be said to be more than enough.
The final question, a dynamic electromagnetic induction problem, requires candidates to set appropriate parameters for calculation.
The topic itself is not very creative, but the difficulty lies in the cumbersome process and the large amount of calculation.
However, after thirty minutes, Xu You successfully completed it.
After solving the last data, Xu You can finally breathe a sigh of relief.
The test papers for the rematch are still very strong!
Far more challenging than the preliminaries.
The fly in the ointment is that the topic seems a bit retro and routine, lacking a certain amount of creativity.
It can be seen that most of the teachers who set the questions took some previous questions and revised them to piece together a test paper.
If Xu You had the opportunity to come up with his own questions in the future, he would definitely not be so hasty.
It is best to come up with some question types that are not even in the book, that will be interesting.
Thinking of the scene of being scolded by the devil behind the examinee's back, Xu You felt an inexplicable evil taste.
"Why does this child seem to be smiling?"
The invigilator also noticed Xu You.
Among the many candidates who were frowning, Xu You seemed very special.
Not only did he have a very relaxed expression, but he also seemed to think of something happy.
Suspicious, the invigilator walked around Xu You's side and looked at Xu You's test paper.
Even every question was fully answered.
"At this level, you should have a provincial one, right?"
The monitoring teacher finally understood Xu You.
If it were me, I would be able to answer this level of test paper like this.
It is estimated that it was already happy.
Of course, after Xu You finished answering the test paper, he relaxed his mind briefly.
Immediately afterwards, it was carefully checked again.
For such an important exam, Xu You would not casually hand in the paper in advance if he was not sure.
As soon as 12 o'clock arrived, the bell rang for the end of the exam.
Many candidates didn't notice the passage of time, so they could only stop writing quickly and hand in the paper.
After collecting the test papers, there was a howl in the examination room.
"It's over, I won't get 0 points in the semi-finals, I feel that every big question is inaccurate." "I feel like my brain is burned out, and I can't remember what I just wrote."
"Half of the questions are not correct." "If you haven't figured it out, you definitely don't need to prepare for the experimental exam, which is pretty good."
Naturally, Xu You would not participate in such meaningless complaints, but walked straight out of the exam room.
He is still waiting for the answer with Hu Shucheng.
This time, Hu Shucheng did not hand in the papers in advance.
Just outside, I ran into Xu You.
"Didn't you hand in the paper early this time?"
Seeing Hu Shucheng in the aisle, Xu You asked with a smile.
"This time we can't waste it. The theoretical and experimental points are cumulative, and every point is very important. Let's go, this time go to the Golden Arch to check the questions!" Because of the rematch questions, the difficulty has increased significantly.
It is impossible to clearly complete the whole process if it is only a verbal examination.
It's better to find a place to restore the answering process.
"Okay, I invite you!"
"Then I won't be polite."
In order to thank Hu Shucheng for his guidance in his experiment, Xu You naturally wanted to treat Hu Shucheng to a good meal.
"Just give me two 1+1 sets."
"Hey, please, let's eat some expensive ones."
Xu You was not stingy, he just ordered two sets of luxurious cheese thick beef burger set meals, and added another set Snacks.
While eating, the two resumed the process of answering just now.