"ah?"
Zhang Litang and Yin Wu did not expect Jiang Yifeng to say this, and immediately looked confused.
"Ah for what?"
Jiang Yifeng looked at the two of them with a serious expression, "This air bag is made of fine silk. You know its value very well. If it burns accidentally, you won't be able to afford the compensation if I sell it."
"..."
Hearing this, Zhang Litang and Yin Wu didn't speak, and looked at the silk on the ground.
Although Jiang Yifeng's words didn't sound good, it was indeed the case. The things Jiang Yifeng asked them to make were sewn with silk.
When they thought of this, they felt a twinge of pain.
A piece of fine silk is worth two taels of silver, equivalent to two months' salary of an ordinary person.
The things Jiang Yifeng asked them to make used hundreds of bolts of silk and were worth more than two hundred taels of silver. They really couldn't afford to pay for it.
"Brother Jiang, Brother Jiang..."
At this moment, Yao Chen's voice came from outside.
Jiang Yifeng looked for the sound and saw Yao Chen, Gong Shuchang and Master Guishou coming over.
Without waiting for Jiang Yifeng to speak, the three of them pointed at what Zhang Litang and Yin Wu were making and asked, "Brother Jiang, is this what you said can fly?"
After saying that, the three of them looked at Jiang Yifeng with eager eyes.
"Um!"
Jiang Yifeng nodded and introduced with a smile: "This thing is called a hot air balloon."
Uncle Ghost Hand's eyes were shining, "Flying like a wooden kite?"
"no the same."
Jiang Yifeng shook his head and explained: "Although both can fly, the principles are completely different."
"what is the difference?"
The three of them were like primary school students eager for knowledge, looking at Jiang Yifeng with wide eyes.
"All right!"
Jiang Yifeng was stared at by the three people and was so frightened that he could only say: "I can't explain the principle of wooden kite to you. I can only tell you the principle of flying hot air balloon."
"Yeah, yeah, yeah!"
The three of them nodded hurriedly.
Jiang Yifeng thought for a while and asked, "Do you know why wood floats on the water?"
"You know, wood is lighter than water."
Gongshu Chang instinctively replied.
Hearing this answer, Jiang Yifeng couldn't help but think of a classic question: Is a pound of cotton heavier or a pound of iron?
So he asked: "Is a pound of wood heavier or a pound of water?"
"of course……"
Just as Gongshu Chang was about to answer, he suddenly stopped and frowned tightly.
When Yin Wu saw that Gong Shuchang was silent, he touched Zhang Litang with his elbow and taunted in a low voice: "Brother, it's a good thing that he is still a master, but he doesn't know the weight of a pound of water."
Snapped!
Zhang Litang slapped Yin Wu on the head, "It's really stupid. They're both one pound, so they obviously weigh the same."
"Uh...it seems like that."
Yin Wu came to his senses and asked in confusion: "Since it's the same weight, why didn't he answer?"
Zhang Litang glanced over and said, "Senior is a master. He must have thought of other questions from this question. There is no point in answering this question."
"What problem did he have in mind?"
Snapped!
Zhang Litang slapped him again, "If I knew, I wouldn't be a master."
…
In fact, when hearing Jiang Yifeng's question, not only Gong Shuchang was thinking, but Yao Chen and Uncle Guishou also frowned slightly.
Because they discovered that Jiang Yifeng's problem was not that simple.
Why does wood float on water?
Their answer was that wood is lighter than water.
The problem is, a pound of wood will also float on a pound of water, and they both weigh the same!
So it follows that the answer that wood is lighter than water is wrong, at least not in the way they understand it.
The three of them thought for a long time, and finally gave up and looked at Jiang Yifeng, "Mr. Jiang, I think my answer is correct, but... forget it, you should just tell us the answer directly!"
Jiang Yifeng smiled and said: "Senior, your answer is actually correct. You just ignored an important unit. If you add this unit, you will understand the truth."
Gongshu Chang asked: "What unit?"
"size."
Jiang Yifeng paused and continued: "If water and wood are of the same size, which one is lighter and heavier?"
"wood!"
Gongshu Chang replied quickly.
"That's right!"
Jiang Yifeng took the opportunity to explain, "Senior just said that wood is lighter than water, but he actually ignored the equivalent of size. At the same size, wood is lighter than water, so it can float on the water."
call……
After Jiang Yifeng finished explaining, he couldn't help but breathed a sigh of relief.
There is no concept of density in this era, so he can only use a language that three people can understand and try his best to explain the concept of density to three people.
"Wood is lighter than water of the same size, so that's why!"
Gong Shuchang, Yao Chen, and Uncle Guishou suddenly realized.
"The measure of mass within a specific volume, I call it density." Jiang Yifeng continued: "And objects with light density can float on objects with high density."
"Density, that's an apt name."
Gong Shuchang nodded in agreement, and then asked: "It's just... what does the density of a hot air balloon have to do with flying?"
Jiang Yifeng said with a smile: "Since water and wood have their own density, does air also have density? As long as the density of the hot air balloon is less than the density of air, it can float in the air just like wood floating on water."
As soon as these words came out, the three people who had been unable to figure it out suddenly understood.
At the same time, Gong Shuchang was secretly glad that he had followed Jiang Yifeng before and learned about the existence of air, otherwise he would not understand the principle of a hot air balloon at all.
If this continues, within a few years, Momen will be able to far surpass the public losers.
"We all understand the truth, but..."
Uncle Ghost Hands, who rarely spoke, looked at the unfinished hot air balloon, frowned and asked: "But in the hot air balloon you made, everything is denser than air, how can it float on the air? "
"Don't worry."
Jiang Yifeng took the hot air balloon drawings and placed them in front of the three people. "The hot air balloon consists of three parts, the top air bag, the lower hanging basket, and the heating device."
"The heating device will continuously heat the air in the hot air balloon. When the air is heated, it will expand, causing the density of the air in the air bag to decrease, generating a rising force. As long as the rising force exceeds the total mass of the hot air balloon, the hot air balloon can be suspended in the air. ”
Gong Shuchang and the other three stared at Jiang Yifeng's drawings, combined with what Jiang Yifeng said, and began to simulate the launch of a hot air balloon in their minds.
The three of them were all smart people. They quickly figured out the reason and couldn't help but be amazed.
"I didn't expect density to have such a wonderful effect. If so, as long as the volume of bronze is made large enough so that its density is less than that of water, can bronze also float on the water?"
Gong Shuchang said jokingly.
The speaker was unintentional, but the listener was intentional. Uncle Ghost Hands suddenly said: "Build a ship out of bronze, which is much harder than a wooden ship."
