Z=4

Z represents the number of nuclear charges of an element.

Which element is the nuclear charge number 4 in the periodic table?

Hydrogen, helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, neon......

It is clear that the nuclear charge number of beryllium is 4.

This problem explains the phenomenon of Be2+ ions being captured during the recombination of a gas discharge through a bunch of symbols, mathematical operations, and physical principles.

After a series of derivation calculations, Shen Qi finally gave the answer: Z=4, which is the beryllium element.

From macroscopic mirages to microscopic ion trapping, most of the world's phenomena can be explained by mathematical and physical methods, which is the beauty of science and the power of science.

Of course, there are paranormal phenomena that human scientists can't explain, and these puzzles are left to non-humans above level 15 to solve.

Shen Qi took 1 hour to complete the first two questions.

The first two questions are indeed difficult, and they are not unmanageable by scholars.

This semi-final exam paper is also naughty, the first two questions are difficult, and the big questions in the back are not too difficult.

20 points for the third question, 24 points for the fourth question, 20 points for the fifth question, 22 points for the sixth question, and 20 points for the seventh question.

Shen Qi spent another hour completing the five calculation questions in the middle.

At this time, two hours passed, and Shen Qi completed seven of the eight questions in the semi-final theory exam.

The last calculation question, with a score of 26 points, is the highest score in the whole volume.

"?" Shen Qi reviewed the question three times in a row, "The big axis question is so simple?

The stems of the last question are:

"Suppose there are 4/5 nitrogen molecules and 1/5 oxygen molecules in the air. ”

"The temperature near the ground is 27°C and the pressure is 1atm. ”

"At an altitude of 10 km above the ground, there is a spherical artificial satellite with a cross-section of 1 square meter, which orbits the Earth at initial velocity. ”

"In the absence of atmospheric drag, the initial velocity of a satellite is just enough to orbit the Earth in a circular orbit. ”

"However, atmospheric resistance is there. ”

"Try to find atmospheric resistance. ”

After Shen Qi reviewed the questions three times, he tried them three more times.

Hehe.

Slag.

Don't think that if you are dressed in a noble and gorgeous coat of 26 points, I won't dare to you.

Shen Qi can finally determine that the big axis question with the highest score is just a paper tiger.

Putting a satellite is a physical phenomenon that combines mechanics and heat.

Because the atmosphere rises slowly, it can be treated as a troposphere for static treatment, where there is a differential relationship between the pressure formed by atmospheric gravity and the decrease of altitude.

The ratio of nitrogen molecules to oxygen molecules in the inscription comes in handy.

As the altitude increases, the atmosphere expands by adiabatic depressurization, and the equation of temperature and pressure can be obtained.

With the help of mechanical knowledge, it is not difficult to estimate the initial velocity of the satellite's motion, which is close to the first cosmic velocity of 7.92 km/s.

The collision between a satellite and an atmospheric molecule can be approximated as an elastic collision between the circular cross-section of the satellite in which the atmospheric molecules are perpendicular to the direction of flight.

Therefore, Shen Qi quickly calculated the result, and the atmospheric resistance of the satellite was:

F=5.5×10^7N

The eight questions in the semi-final theory exam involve optics, quantum theory, electricity, electromagnetism, mechanics, acoustics, preliminary astrophysics, and heat.

"The teacher who wrote the question regarded himself as God. Shen Qi checked the test paper once, and then checked it again.

Although there were still 30 minutes, Shen Qi did not rush to hand in the papers, check, continue to check, and spent three hours of answering time.

"If you can't get 160, how can you face my ancestor Shen Gong?"

160 is the full score of the semi-final theory test paper, and Shen Qi took out all his strength to correspond to this test paper, aiming to get 160.

After the game, Mu Rong gathered the 13 players who participated in the semi-final to understand the situation.

"It's difficult!" Bai Lingye shouted for my life.

"It's hard. Lin Xingyu's face was solemn.

"It's difficult. Shen Qi said truthfully.

"Shen Qi, you didn't submit the paper in advance this time. Mu Rong felt that the situation was not optimistic.

"The first two questions are a bit complicated. Shen Qi said.

"Hey, I didn't write the fill-in-the-blank question, and I couldn't deduce the trajectory equation, and this question obviously touched the blind spot of my knowledge. The quantum theory of the second question is even more perverted, I wrote it blindly. The satellite question of the last question, counting the atmospheric resistance, I obviously have an impression, but I was confused as soon as I took the exam, I am a useless salted fish. Bai Lingye said bitterly.

"Actually, what Mr. Mu said is that we didn't learn well. Lin Xingyu looked for problems from himself.

"I may not be able to score 80 points in the theory test with a score of 160, forget it, I don't have to take the experimental questions, and it's useless to take the test. Bai Lingye said dejectedly that she was promoted to the national finals, won the national award, entered the physics experimental class of Yan University, and was finally left by Yan University...... This is too difficult to do, Bai Lingye is also a primary school bully in their class, and on a stage similar to the provincial exam in the CPhO semi-finals, he feels that he is no different from a scumbag.

"Remember the classmates, never give up hope!" As the team leader, Mu Rong must be optimistic, although she is a little pessimistic in her heart.

Nearly 1,000 players in the province participated in the semi-finals, according to the practice of Nanyue Province, and finally selected no more than 10 people to represent the province to participate in the national finals, because the experimental questions have not yet been examined, Shen Qi does not dare to guarantee 100% that he can enter the national finals, he comforted the two junior brothers: "Lin Xingyu, Bai Lingye, you are only in the second year of high school, and you will have a chance next year." Teacher Mu is right, never give up hope, even this year, don't give up hope, the one who doesn't report hope is a salted fish, at least we can fight on the experimental questions. ”

"Hmm!" Lin Xingyu nodded heavily, he stubbornly let himself hold on to a glimmer of hope and not let go.

"Okay, everyone has worked hard, go back and have a good rest, adjust the state, and disband. Mu Rong issued an order to disband, and everyone went back to their homes.

94% of the contestants were eliminated in the preliminary round, the number of remaining contestants decreased sharply, and the grading of the theoretical test papers of the CPhO semi-finals was progressing quickly.

One day later, the semi-finalists will be able to check the results of the semi-final theory test on the Chinese Physics Competition website.

Shen Qi used his mobile phone to check the score, and his mood was a little apprehensive.

Enter your test number and click "Search".

The mobile phone scoring system shows:

Name: Shen Qi

School: Nangang No. 2 Middle School

Exam number: 10201XXX

CPhO semi-final theory test score: 159

After seeing the results of 159, Shen Qi was shocked: "Who ...... Who the hell is embarrassing me? Why did you deduct a point from me?"

Full score for this kind of thing, if you don't taste it, you will be addicted to it once you taste it, just like smoking crow pian.

CPhO won two "full points minus one point" in the preliminary and semi-finals, and no one can accept this cruel reality.

"In this way, even if I get a perfect score of 40 points for the experimental questions, the total score in the semi-finals will be 199 points at most. I...... I may not be able to enter the national decision. Shen Qi felt the pressure.

"Brother, you are the thinking of a scholar, oh no, no, the thinking of a god. The Xueba test is ninety-nine, and the Xueshen has been full for a long time, but there are several Xueshen in the province, and the score of 159 in the theory test is very high! Do you think everyone can get a full score in the theoretical test?" Lin Xingyu scored 130 points in the theory test, and he was quite satisfied, and it had exceeded his estimate.