Mr. Bao and his son: Only use Stankang for hair oil

Chapter 47 I'm a Genius

"We'll wait. I'll go to the toilet first and then come back to answer your questions. Guo Chun, let's go."

Bao Guowei did not refuse An Shuzhen's question, so as not to make others think that he was unreasonable.

"OK, all right."

An Shuzhen nodded, turned her head and continued thinking about the question.

……

"No, this school is like a disease. You have to have such long classes in the morning. When I came here today, I drank a bowl of sour plum soup. After one class, I was suffocated to death."

After walking out of the classroom, Guo Chuncai cursed and complained, and even said dirty words.

"Then you should drink less water in the morning from now on. You have already failed the grade. Aren't you still used to this routine?"

"If this class hadn't been for someone named Song, I would have raised my hands and yelled to go to the toilet. How could I wait until now?
Moreover, this holiday has passed, and my schedule has long been changed. I usually read books, read newspapers at home, and have people waiting on me. I can also find people to play basketball with, and I can also go shopping... Anyway, it is happier than going to school. How much. "

While the two were chatting, Bao Guowei noticed a shadow on the wall next to him, following the two of them. He knew it was Chen Jinhua without looking back.

Chen Jinhua yawned and followed the two of them feebly. He was still a little sleepy, but he had to accompany Guo Chun when he left the classroom. What if Guo Chun felt that he had changed his mind:
"Guo Chun, why don't we go to Songhe Tower for dinner tonight? We Himalayan team members haven't been to Songhe Tower for a dinner in a long time."

Guo Chun ignored him. If Bao Guowei had said this, he would still consider agreeing. Chen Jinhua's words were just a fart.

Chen Jinhua was always very persistent about Songhe Tower. Bao Guowei had only known him for a day and had already heard him mention Songhe Tower several times. He didn't know what was so attractive about it.

Just after class, students all like to come out and do some exercise. There are already many students in the corridor. There happened to be a female classmate walking by. She was wearing a pink scarf and holding a book in her hand. She looked good.

When Guo Chun saw the female classmate, he couldn't help but want to tease her. He jumped up slightly, made a shooting motion, and whistled at her. The girl immediately blushed and ran away.

Seeing this, Bao Guowei inadvertently distanced himself from Guo Chun: This kind of behavior was really embarrassing, and it almost made him ashamed to be in the company of Guo Chun.

There are toilets on every floor of the teaching building, only a few dozen steps away from the classroom.

However, it is easy to have diarrhea in the morning, especially when the weather is cold in autumn, and now it is almost winter...

The three of them almost covered their noses with their clothes and escaped from it. The smell there was simply degrading.

"I will never come here again. I still have to go to the teachers-only toilet to use it. There are fewer people there and it is much cleaner."

Probably because he had been holding his breath for a long time, Guo Chun was still a little unable to speak slowly, and he was still breathing heavily when he spoke.

……

Returning to his seat, Bao Guowei found that An Shuzhen was still thinking seriously about which question, so he took out his pencil and poked her with the back of his head.

"Which question? Ask it."

An Shuzhen turned her head, pointed at the handout and said, "This is the way. It feels so difficult."

This question is at the end of the back of the handout, an expansion question with a picture.

Just by looking at the picture, Bao Guowei knew there was something wrong with this question. According to the teaching progress, this question appeared a little early:

A long wooden board with mass M = 1 kg and length L rests on the horizontal plane. A small object with mass m = 1 kg is placed on the left end (can be regarded as a mass point). The kinetic friction coefficient between the small object and the wooden board μ = 0.3. The distance between the wooden board and the horizontal surface The dynamic friction coefficient μ′=0.1.
Give the small block a horizontal pull force of F=6N to the right, causing the small block to accelerate to the right relative to the wooden board. The gravity acceleration g=10 m/s square. Find the acceleration of the small block and the wooden board. (Kinematic friction factor is the ratio of sliding friction to positive pressure)
After reading the entire question, Bao Guowei frowned. This question seemed a bit complicated at first glance. It was probably as difficult as the ordinary physics questions in future college entrance examinations.

It was only the first day of school, and Teacher Song asked such a question, which was really outrageous.

The only difficulty in this question is the introduction of friction. The knowledge point of friction is relatively difficult to understand.

Not to mention that this question is essentially about three objects frictionally moving with each other in an inertial system, which is still quite troublesome to analyze.

Not only is the question a little out of scope, but the second question is also a bit sinister. Those who don’t understand Niu’s Second Law can easily regard small objects and wooden boards as a whole and substitute them into Niu’s Second Law.

Bao Guowei frowned and thought for a while, then took out his outline, took out his pencil, and wrote on it. His pen was very fast, and after a while, the entire outline was filled.

An Shuzhen was sitting opposite and couldn't see clearly what Bao Guowei wrote. Guo Chun, who was sitting next to him, looked at it curiously. The pile of letters in front of him made him dizzy. When he looked at Bao Guowei, his eyes suddenly It becomes like looking at a monster.

"First of all, the gravitational acceleration g=10m/s squared means that the gravity exerted on the object is 10N/KG. I won't tell you how to derive this result. Just remember it. The teacher will definitely explain it later."

Pointing to the conditions in the question, Bao Guowei said to An Shuzhen.

It's not that Bao Guowei doesn't want to teach her. Just the derivation that the unit of acceleration is meters per square second might be enough to stun her. It involves several letter unit transformations. If you're not familiar with the formulas, you won't be able to understand it.

An Shuzhen glanced at Bao Guowei and nodded, feeling a little confused.

"Since the teacher didn't tell you...how did he know? If he was self-taught, then he would be too good!" An Shuzhen thought to herself, quietly listening to Bao Guowei's next words:

"That is to say, the positive pressure of the small block on the long wooden board is 10N, and the kinetic friction factor is 0.3. Considering that the small block is given a horizontal pull force of 6N to the right, which is greater than the sliding friction, the friction force of the small block on the long wooden board is 3N, the direction of friction is opposite to the direction of its motion, do you understand?”

Bao Guowei took out a pencil and pointed at the small wooden block, drew an arrow to the right on the small wooden block, wrote 6N, marked F, and drew an arrow to the left under the small wooden block, written 3N marked f.

This is called force analysis, a necessary skill in physics. As an old saying goes, when you are in doubt, first construct a rectangular coordinate system and then analyze the force.

Questions that were originally difficult to solve can often be solved directly after analyzing the stress situation.

From the sun to the moon, to atoms and electrons, this operation is very easy to use. Every physics teacher in the future will teach it, and it will last almost throughout the students' entire high school physics career.

An Shuzhen looked at the picture drawn by Bao Guowei seriously and frowned slightly. She thought carefully about Bao Guowei's words and thought for a while before she figured out the connection.

"I... figured it out."

An Shuzhen said softly, and her words surprised Bao Guowei.

Bao Guowei thought that An Shu really couldn't understand. For students who had only taken one big class, this question could be said to be hellishly difficult.

It seems that this female classmate is at least clear-minded and has some talent in physics.

After all, Teacher Song's big class can be described as an outline-style rapid infusion of knowledge points. If An Shuzhen can even gain a preliminary understanding of it, she is already ahead of most people.

As for Guo Chun next to him, he was confused now. After hearing An Shuzhen say that he understood, he felt that his self-confidence had been hit, and he felt that he had become a little less confident.

Bao Guowei then spoke:
"Okay, now that the force has been analyzed, it is time to calculate the resultant force. The small object is subjected to: pulling force, friction force, gravity, and supporting force. Calculate it. You can solve the first question by relying on Newton's second law formula. You Try to figure it out.”

An Shuzhen was still a little unfamiliar with formulas. After all, Teacher Song taught too many things in this class, so she could only look through the Gewu book to find the formulas.

"The sum of F on the horizontal plane is equal to the pulling force minus the sliding friction force. The two forces in the vertical direction are balanced. Substituting into the equation of Cow's Second Law, we can calculate that the acceleration of the small wooden block is...three meters per second?"

An Shuzhen said cautiously, her face full of expectation, hoping that Bao Guowei's answer was correct.

However, her answer is not completely correct. The numerical value is correct but the unit is wrong.

"If you get four points for this question, you will be deducted at least one point. The unit of acceleration is meters per square second, and the unit of speed is meters per second. Why is it meters per square second? This unit involves the definition of acceleration. , the teacher will definitely lead everyone to deduce it later.”

Bao Guowei said without mercy, but this already made An Shuzhen very happy: she just made a wrong unit, and the value was still correct.

"Let's talk about the second question next. The effects of forces are mutual. Friction is the force that hinders the movement of objects. Who is blocking the small wooden block?"

"Long plank."

"Yes, since the long board blocks the small block, and the small block receives a friction force of three N to the left, so based on Cow's Three Laws, does it follow that the long board will also receive a friction force of three N to the right?"

Bao Guowei started writing arrows on the long wooden board again.

"……Correct."

"The long wooden board is subject to a total of four forces: gravity, support force, the friction force produced by the small wooden block, and the friction force produced by it on the ground... The analysis is almost done at this point. There is one thing that needs to be paid attention to, that is, do not put it on the ground. The two objects are treated as one whole because..."

When Bao Guowei talked about this, he got into a state of mind and began to talk endlessly about the common mistakes. As he talked, several students around him were also attracted to him and listened to Bao Guowei in stunned silence. A language they don’t understand.

"Understand?"

"..."

An Shuzhen didn't reply this time. She just frowned and thought seriously. Looking at Bao Guowei's full handout, it seemed that she had gotten into trouble.

"Bao Guowei, I have a hard time listening to these things. How do you know so much?"

An Shuzhen thought for a while but couldn't figure it out. She couldn't help her curiosity and asked Bao Guowei.

"Because I am a genius. I can integrate the knowledge in just a few books of inquiry. The world of genius is so simple and unpretentious.

You can understand the first question, which is already very good and worthy of praise. Come on. "

Bao Guowei began to brag, and subconsciously wanted to pat An Shuzhen's shoulder to cheer her up. Just as his hand was about to touch her, he retracted it again.

I almost broke a taboo. The Republic of China was different from later generations. Girls couldn't be patted on the shoulders casually.

　Isn't it the whole heroine thing?Leave a message. . .

　　
　
(End of this chapter)