Chapter 28: Candidate, why are you laughing?
"First, establish a spatial rectangular coordinate system, and then use the center of gravity formula to find the position of the teacup's center of gravity."
For Xu You, who also takes math competition into consideration, such operations are too basic.
In less than a minute, Xu You found the coordinates of the center of gravity of the teacup in this coordinate system.
"Just make sure the center of gravity of the teacup is as close to the stool as possible."
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 cross-section and converted it into plane force.
And according to the trigonometric function relationship, torque balance and other conditions, the formulas are listed one by one.
"Combining equations 7, 10, and 11, we can find the final change in force."
In less than ten minutes, Xu You completed the entire process of the first question.
Based on the 3-hour exam time, the time left for each question is about 20 minutes.
Xu You's speed gave the exam a good start.
This is the key to the difficulty of the rematch.
Many questions can probably be answered if the candidates are given enough time .
But the difficulty lies in being able to complete the answers within the specified time.
When Xu You finished the first question, some students had just started to build the system and didn’t even know how to calculate the height of the center of gravity.
This has a lot to do with the fact that their mathematical knowledge is not solid enough.
It is already very difficult to find time to prepare for a competition in addition to normal high school studies.
There are not many students like Xu You who can prepare thoroughly for both competitions at the same time.
The second question is a relatively simple geometric optics question.
Of course, it’s for Xu You.
It can be solved by using the equal optical path property. It is a relatively routine problem.
Questions three and four were not too difficult, except that they required a little more calculation. Xu You spent no more than twenty minutes on each question.
The questions of questions five and six are obviously starting to become longer. If you don’t look carefully, they look like IPhO and APhO.
For example, question 5 involves the concept of laser cooling, and generally only IPhO and APhO will 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 focus is on the Doppler effect of light and resonant absorption.
After finishing the first six questions, Xu You looked at the time and saw that there was more than an hour left.
This speed is even faster than Xu You planned.
This will give Xu You enough time to tackle the last two big questions.
These last two big questions are often the most difficult ones.
The other students, who were faster, had already finished the fifth question.
Slowly, I just started answering the third question.
And that doesn't include some of the skipped parts.
Of course, there are still many students in the rematch who were completely defeated by the questions and chose to withdraw from the exam early.
They could only regretfully admit that competition was not their battlefield.
They are just slightly better at physics in ordinary high schools, so they should just go back and prepare for the college entrance examination.
"Question seven isn't that difficult, actually."
A dynamics problem, mainly examining the force analysis of rigid bodies.
The thinking difficulty is medium, and it can only be said that the amount of calculation is slightly larger.
For the three small questions, Xu You listed more than twenty formulas.
Although calculators can be used in physics competitions, Xu You still does some simpler calculations by hand.
This is also an experience summed up by Xu You.
Unless the numbers are extremely large or the equations are extremely difficult to solve, pen and paper calculations may be more convenient than using a calculator.
In twenty-five minutes, Xu You completed the entire process of question seven.
There are more than forty minutes left, which is more than enough to solve the last question.
The final question is a dynamic electromagnetic induction problem, which requires candidates to set appropriate parameters and perform calculations by themselves.
The question itself is not very creative, and the difficulty lies in the fact that the process is rather complicated and requires a lot of calculations.
However, after thirty minutes, Xu You successfully completed it.
After solving the last piece of data, Xu You could finally breathe a sigh of relief.
The exam paper for the rematch is still very exciting!
It is far more challenging than the preliminary exam.
The only drawback is that the title seems a bit retro and formulaic, lacking a certain creativity.
It can be seen that the teacher who set the questions probably took some previous questions, modified them, and put together a test paper.
If Xu You had the chance to set questions himself in the future, he would definitely not be so careless.
It would be better to come up with some question types that are not even in the book, that way it would be more interesting.
Thinking of the scene where the examinees called him a devil behind his back, Xu You felt an inexplicable sense of evil pleasure.
"Why does this child seem to be smiling?"
The invigilator also noticed Xu You.
Among the many candidates with sad faces, Xu You stood out.
Not only did his expression look extremely relaxed, he also seemed to be thinking about something happy.
With suspicion, the invigilator walked beside Xu You and looked at his test paper.
I answered every question well.
"This level should be first in the province, right?"
The monitoring teacher finally understood Xu You.
If it were me, I would be able to answer a test of this level like this.
I guess he would have laughed out loud a long time ago.
Of course, Xu You only relaxed his mind for a short time after finishing the paper.
Then , he started to check carefully again.
For such an important exam, Xu You would not hand in the paper early if he was not sure about it.
At 12 o'clock, the bell rang, signaling the end of the exam.
Many candidates did not notice the passage of time and could only stop writing and hand in their papers quickly.
After the papers were collected, there was wailing in the examination room.
"It's over. I hope I won't get 0 points in the rematch. I feel like I didn't answer every question correctly."
"I feel like my brain is fried. I can't even remember what I just wrote."
"I didn't figure out half of the questions, so I definitely don't have to prepare for the lab exam, which is good."
Xu You naturally would not participate in such meaningless complaints, but walked straight out of the examination room.
He was still waiting to check answers with Hu Shucheng.
This time, Hu Shucheng did not hand in his paper early.
I happened to be outside and ran into Xu You.
"You didn't hand in the paper early this time?"
Seeing Hu Shucheng also in the aisle, Xu You asked with a smile.
"Don't waste time this time. Theory and experiment scores are cumulative, and every point is important. Let's go to McDonald's to do the test this time!"
Because the difficulty of the rematch questions was significantly increased.
If you just discuss the topic verbally, you will not be able to complete the whole process clearly.
It would be better to find a place to restore the answering process.
"Okay, I'll treat you!"
"Then I'll be welcome."
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+1s."
"Hey, it's my treat. Let's have something expensive."
Xu You was not stingy and insisted on ordering two deluxe cheese thick beef burger sets and added a snack.
While eating, the two of them replayed the solution process they had just done.
