A few minutes later, Cheng Chumo stood at the edge of the house with a sad face, ready to jump again, there was no way.

In the simple multiple-choice question of jumping from the roof once after being beaten by Cheng Xiang or taking the initiative to jump once, Cheng Chumo chose the latter.

"Observe carefully this time and see if it lands at the same time!"

"Good!"

Lu Su looked at his classmates beside him, although he couldn't bear to fall Cheng Chumo again, but thinking of Cheng Chumo's rough skin and thick flesh, it seemed that it didn't matter if he fell once or twice, so he followed the position behind, and waited with wide eyes.

"Sister, I really jumped!"

Cheng Xiang was also waiting on the side, although Cheng Xiang believed in Yu Zhiqian very much, but some things were better to see was believing!

"Jump!"

Cheng Xiang waved her hand and signaled her brother to jump faster, she still had to rush to play mahjong with the crown princess Li Shishi and others!

"I really jumped!"

"I'll knock you down again!"

Seeing that Cheng Chumo had some ink, Cheng Xiang got up and wanted to make a move on Cheng Chumo, Cheng Chumo was immediately ready to jump, and when his sister did it, he didn't fall down, but was beaten and then thrown down.

At this time, Yu Zhiqian, who was holding a bunch of grapes in his hand, shook over leisurely, and after seeing Cheng Chumo standing on a high place, he asked with some curiosity: "Cheng Chumo, why are you standing so high?" ”

"Your Highness! I ......"

"Don't get down quickly, if you fall, this palace is not responsible for the medical expenses!"

At this time, Cheng Xiang walked up to Yu Zhiqian and said what happened, Yu Zhiqian touched Cheng Xiang's head: "Okay, don't mess around with your brother, if your head hits the ground, maybe someone will die!" ”

Yu Zhiqian immediately asked Cheng Chu to be silent, this small building is about more than ten meters high, if it falls, it will really kill people, let alone ten meters, it is a wall of less than two meters, and falling down headfirst will also kill people.

When I was in college, there was a classmate, there was a wall about 1.8 meters from the cafeteria to the dormitory, Yu Zhiqian's height of 1.83 meters was about the same height as the wall, Yu Zhiqian didn't remember the name of the goods, but in order to save a few steps of time, he climbed over the wall, but his feet slipped, his head hit the ground, and the person was gone......

After Cheng Chu was silent, Yu Zhiqian glanced at it: "Okay, you don't have to study it, go to the school, I'll tell you the reason!" ”

After finishing speaking, Yu Zhiqian walked up to Cheng Xiang and stared at Cheng Xiang with a cold face: "You, you, it's not me who said you, let you not mess around, if Cheng Chumo falls out of the way, see what you do!" ”

Cheng Xiang looked at Yu Zhiqian, and pulled the corner of Yu Zhiqian's clothes with some grievances: "The concubine knows that she is wrong!" ”

"Go back, don't catch a cold outside!"

"The concubine retires!"

Yu Zhiqian glanced at Mama Rong and Peach Blossom: "Take care of Concubine Cheng!" ”

"Whoa!"

In the school, all the students were very quiet, waiting for Yu Zhiqian's arrival, before this group of people didn't know what Tsinghua Garden was teaching, but now they knew a little bit, especially the experiment in the morning, which made them feel a little incredible.

Yu Zhiqian walked into the school and looked at the people below, this group of students went to experiment by himself just now, which shows that this group of students has the spirit of exploration, this quality is very rare, and he handed over the theory to this group of students, and this group of students went to operate.

"Ahem, ahem, everyone saw this morning's experiment, does anyone know why?"

After Yu Zhiqian finished speaking, he slowly glanced down.

After waiting for a few minutes, no one answered, the corners of Yu Zhiqian's mouth curled slightly, no one knew, so he could start pretending.

After setting up the blackboard, Yu Zhiqian took out his small ring ruler and glanced at the students below: "In the morning experiment, you have all seen it, and the result is that two objects with different masses fall from a high place and fall to the ground at the same time, this law is called the law of free fall!" ”

"The law of free fall?"

A group of students looked at Yu Zhiqian in confusion, many people had already started to copy, Yu Zhiqian waved his hand: "Don't copy it first, I'll tell you about this law of free fall!" ”

After Yu Zhiqian finished speaking, he took out the prepared props: "This law of free fall refers to the fact that two objects fall at the same time and will land at the same time, no matter what the object is, it will be like this!" ”

Hearing Yu Zhiqian's words, Yu Chi Yulin immediately stood up: "Your Highness, brushes and paper are not good!" ”

After finishing speaking, he immediately put down the brush and paper at the same time, and the paper flew lightly for a distance before slowly landing on the ground.

Yu Zhiqian looked at Yu Chi Yulin, although this guy is five big and three thick, he likes to think, and he can also ask questions, he is a good seedling.

"This is because there is buoyancy in the air, and there is resistance and so on, and what I said is a precondition, that is, in a vacuum!"

"Vacuum?"

"Yes, vacuum refers to the environment below one standard atmosphere, I will give you a vacuum experiment in the future, and you will know when the time comes, today's experiment can prove one point, that is, two ......"

This group of students listened to the fog and was exposed to a lot of new vocabulary.

"Your Highness, what do you mean by air?"

At this time, Lu Su slowly raised his hand, Yu Zhiqian patted his head, almost forgetting that this group of students didn't know what air was, Yu Zhiqian smiled, breathed hard, and then exhaled: "The air is around us, when we breathe, it is the oxygen that is exhaled into the air......"

"Your Highness, I still don't understand!"

Yu Zhiqian shook his head helplessly, found a paper bag, and then pulled it hard, and then sealed the mouth of the bag: "The gas in it is air, the reason why we can live is because of these, animals and plants are the same, this is what you will study in the future!" ”

"Your Highness, what is the buoyancy?"

"Buoyancy is an invisible force, can you all swim?"

"Yes!"

"Then why are you able to float when you're in the water?"

This group of students, you look at me, I look at you, I don't know how to answer for a while, Yu Zhiqian waved his hand: "That's because water is buoyant, and you can swim in the water, that is, use the buoyancy of water!" ”

The group of students nodded thoughtfully, and Yu Zhiqian continued: "In addition, the air is also buoyant, why can the paper kite you put fly up?" ”

At this time, Cheng Chumo raised his hand very high: "Your Highness, I know, it's because of the wind!" ”

"Wind is only created when the air moves, but it is actually because the air is buoyant!"

"Your Highness, why can't we fly?"

“……”

"That's because the mass of man is greater than the buoyancy of the air, so it can't fly, and the earth has a gravitational ......"

A group of students kept asking questions, and the questions became more and more profound, Yu Zhiqian was almost asked what to do, and sighed long: "Okay, you know too little now, and now I tell you that you can't understand it, and there are some things that you need to explore by yourself!" ”

"Well, the first thing you have to do now is to learn math well, and to measure the density of everything you can see and know!"

Hearing Yu Zhiqian's words, Li Bai nodded silently, but Yu Zhiqian pointed at him: "Li Bai, especially you, I will give you some tasks, you go and measure the density of water, you must be accurate!" ”

"Huh?"

Li Bai was stunned for a moment, the density of water, and couldn't help but touch his head a little anxiously: "Your Highness, how to test the density of water?" ”

"To test the mass of an object, divide the weight of the object by the volume of the object, and you can figure out the method yourself! Except for Li Bai, everyone measures at least five kinds of objects, and hand them over to me in three days! ”

Yu Zhiqian simply wrote a formula for them, and announced that the class would be over, and what Yu Zhiqian could teach this group of people was roughly junior high and high school knowledge, as for college knowledge, maybe Yu Zhiqian needed to go to Zhou Gong and ask, when he was in college, when Zhou Gong played chess with him, did he listen to what his teacher said!

When Yu Zhiqian announced the end of class, he quickly left the lecture hall, and he must prepare for class well after going back, otherwise, this group of questions and questions will be really difficult for him to handle, and the knowledge in his head is even not enough to deal with this group of students.

After Yu Zhiqian's class ended, a group of students looked at each other, today's day was a big shock for them, and some of them had not yet reacted to what was happening.

Yu Chi Yulin grabbed it with his hand, with a puzzled expression.

"Wei Chi, what are you grabbing?"

"I'm grabbing air, Your Highness asked us to measure the density of objects, and I think air should be able to measure too!"

"How do you measure air?"

The people around were stunned, some people didn't even understand the above formula, Li Bai has begun to scratch his hair now, the prince asked him to measure the density of water, how to test water? Water is invisible, how to calculate the volume?

"It's so hard!"

"But I don't understand, what's the use of learning these things?"

"I don't know, but the crown prince is so smart, it should be useful, I heard that His Royal Highness the Seventh Prince is working on a carriage that can run without a horse!"

"The Seventh Prince? That's right, we can go and ask the Seven Princes! ”

The eyes of a group of students immediately lit up, instead of thinking about it here, it is better to find someone who will study it, a few people who have a good relationship with Lao Qi, quickly pack up their things, and prepare to visit the Seven Princes.

At this time, Cheng Chumo looked at the paper in front of him, and suddenly there was a flash of inspiration, the density of the paper seemed to be measurable, but a piece of paper seemed to be unable to weigh it!

Everyone had their own doubts, and they left the royal palace in groups of three and two, and hurried home.

Cheng Chumo had just gone home, Cui Shi was already waiting, and after seeing Cheng Chumo coming back, he immediately called Cheng Chumo in.

"I went to study with His Royal Highness the Crown Prince today, what did I learn?"

"Back to my mother, I learned a lot of new things, but my son didn't understand it!"

"Oh? Tell me about it! ”

Hearing his mother's inquiry, Cheng Chumo roughly said what Yu Zhiqian said today, and Cui Shi was also stunned after hearing it, he thought that the prince would teach some famous classics, but he didn't expect to talk about something he didn't know at all.

"Have you figured out what you're going to measure?"

Cui Shi looked at his son curiously, he really didn't understand those things.

"Mother, I want to measure paper, wood, and stone!"

Cheng Chumo thought for a long time and said five things, but he frowned: "But I still don't understand, this paper is so light and thin, you can't measure the weight of the paper when you put it on the scale!" ”

After Cui Shi heard this, then the whole person laughed: "My stupid son, you can't measure a piece of paper, what about ten pieces of paper, a hundred pieces of paper?" What about a thousand? That's not fine! ”

After Cheng Chumo heard this, his eyes lit up, and he patted his head vigorously, he was really a fool, such a simple question had bothered him for so long.

But soon, Cheng Chumo was bothered by a new question: "How to calculate the volume of the paper?" ”

"His Royal Highness the Crown Prince didn't teach?"

"Teach, it seems to be length, width and height or something!"

"You can ask the carpenter about it, they should know!"

"Yes!"

On this side, Cheng Chumo is ready to measure, on the other side, a group of people came to Lao Qi's mansion, such as King Jing's third son came to Lao Qi's mansion with a few friends, at this time Lao Qi is studying his own steam engine, and now Lao Qi's steam engine has a certain model, but the power has been very low, and it can't drive anything.

"His Royal Highness the Seventh Prince!"

Everyone saluted Lao Qi one by one, and Lao Qi glanced at it: "Do you say measuring the density of objects?" ”

"Yes, this is the homework that His Royal Highness the Crown Prince gave me!"

Lao Qi thought for a while: "I won't be able to do this, but I glanced at your formula, it should be very simple, for example, this piece of wood is one cubic meter and weighs ten catties, so the density is 10 catties per cubic meter, it should be like this, right?" ”

"Then may I ask Your Highness, how should this volume be calculated?"

“……”

Yu Zhiqian became a teacher for the first time, and it cannot be said that Yu Zhiqian's teaching is not carried out, and Yu Zhiqian's teaching is also more conscientious, but there are some places that he has not noticed.

However, after Lao Qi gave a detailed explanation, this group of people finally understood and knew how to calculate, and they left one after another, preparing to return home to complete Yu Zhiqian's task.

In the past three days, Chang'an City has been a lot quieter, and the sons and daughters of the noble families who often come out of various profligacies have surprisingly not come out, but are constantly calculating the density of various objects at home, and some houses have been made a lot of noise.

And Yu Zhiqian is at home with his two daughters-in-law and a concubine, the crown princess has recently lost weight very successfully, her weight has successfully reached 125 pounds, and it is still declining.