Yep

After returning from the amusement park, Xu Jianian started running to the city library to find the secret to making a roller coaster toy.

The city library is three floors high, and the facilities inside are a bit old. The iron frames of the windows are green, and there will be a "squeak" sound when pushed, which is very harsh in the quiet library, and makes people feel uncomfortable. Good associations, such as a mouse crawling across a wall.

Most of the time in summer is bright, the sunlight flows through the two bauhinia trees with sparse leaves outside the house, then passes through the transparent glass, and finally falls on the wooden tables, chairs and bookshelves, illuminating the old and new books and the moth-eaten of wood.

The fine dust floats up and down in the light path, like dull bugs flying around in the air.

Xu Jianian searched around in the library, and finally found the entry for "roller coaster" in the area labeled "Physics". To his surprise, the entry for roller coaster actually had a lot of content.

He saw the first sentence in the book, "The roller coaster train itself has no motor: for most of the running process, the train moves by gravity and momentum."

What are gravity and momentum?

Isn't the roller coaster relying on the wind to blow it up?

Xu Jianian thought about it carefully, and quickly overturned his conclusion: No, when the roller coaster was going down, the wind blew me up, but the car was still going down, so the roller coaster was going forward against the wind. The wind didn't push the car forward, but hindered it. Drive forward!

So gravity and momentum...

He ran back to the bookcase again, found a copy of "Fundamental Physics", looked through it, and this time quickly found what he wanted.

During the last period of this summer vacation, Xu Jianian fell into this kind of life:

A rickety table in the corner, several books on the table, a pen, a few sheets of paper, the light that always shines on his cheek and the books, and most of the time silent books museum.

A certain magnificent and magical world began to unfold before his eyes bit by bit through the black and white pages.

When you are deep in time, the time is long and frustrating; after you are out of time, the time is so fast that you are frightened.

In a blink of an eye, the long and boring summer vacation is over.

In the first few days after the end of the summer vacation, everyone was full of enthusiasm. No matter when class was in or out, there would always be buzzing noises in the classroom, like a hundred flies circling around your head, even if there was a "snap" sound of the ruler on the podium. It's no use knocking on the verge of breaking.

Every time the teacher couldn't suppress the noise, Xu Jianian would always pull out a physics extracurricular book from the hole in the table, and fell into trouble on his own:

During the summer vacation, according to the contents of the book, he knew the basic principles of the roller coaster, and understood that the initial power of the roller coaster comes from the launching device, and the subsequent power comes from gravity and momentum.But in the roller coaster device he made by himself, the car can't always shuttle perfectly around the ring track. Maybe the friction of the track he made is too strong, and the spring force he made is too weak, so that the car has not yet reached the highest point of the ring track. When it slipped.

However, he succeeded in experimenting with the same theory.

He found miraculously that when he swung the water glass in a circular motion, the water in the glass would not fall down.

So what should be done so that the car can have more power?Wouldn't it be better to add some lube to the wheels to reduce drag?

One week after the start of school, the laxity and excitement brought to the students by the two-month summer vacation finally eased, and Xu Jianian finally overcame all the problems and completed a simple roller coaster!

It's not a problem with the lubricating oil. The experiment with lubricating oil still failed.

On the day when the experiment was successful, he was playing glass bead bullets next to the track. During a celestial girl scattering flowers, several glass beads fell on the track he had assembled. Most of the glass beads jumped out, but a certain one came out The direction of the beginning of the track slides all the way, especially turning around the ring track smoothly, and finally lands at the end.

Success came so unexpectedly!

The excitement brought about by the success of the experiment didn't really dissipate until the day when Xu Jianian's school organized an autumn outing.

On the day of the autumn outing, a total of [-] buses stopped at the school gate neatly, carrying students from eight classes to the campsite.

In the south in September, the weather is still as hot as summer.The bright sun hangs high in the sky, swaying unscrupulously with overwhelming enthusiasm, the light falls on the hands, like a small flame approaching the skin.

But all the heat pales in comparison to the children's enthusiasm for autumn outings.

They arrived at the campsite at 10:30 noon.It was a very spacious place, with the creek and woods in the distance, and the brown soil occupied a large part of the line of sight. Visually, it was as big as a school playground.On the soil, the stone fire pits are in order, and each stone pit is five steps away from the adjacent stone pits. Looking around, the dot matrix is ​​in order, which makes people feel relaxed and happy.

Under the leadership of the teacher, everyone looked for their own stone pit. The teacher followed and shuttled through it, holding a loudspeaker and emphasizing loudly: "Pay attention to safety, be careful of the flames, and the group that still can't light the fire after half an hour remember to ask the teacher—"

The teacher spoke, and Xu Jianian also spoke.

Xu Jianian said to the group members: "Let's light the fire too."

Ding Ding raised his hand: "I have a lighter and a candle!"

Xu Jianian has recently been obsessed with experiments and couldn't extricate himself. He said seriously: "There is a way to start a fire in the wild. A good adult can start a fire without a lighter."

Others wondered: "How do you light a fire without a lighter?"

Xu Jianian: "Drilling wood to make fire!"

Others were a little in awe, but also a little curious: "Then you try?"

Xu Jianian immediately got ready!

He first built the fire, and stuffed fine firewood in the stone pit, and then put ordinary firewood end to end, and pressed it on the top of the stone pit in the shape of "well". After building three or four layers, he stuffed firewood in the middle. Thicker twigs, filled with easy-to-burn paper balls, feathers, and fine wood chips, were scattered over the fire, just in case.

The beautiful pyre made the people in the same group have confidence in Xu Jianian.

At this time, Xu Jianian began to prepare to light the fire.

He first tried to make fire by drilling wood.

Take a wooden board that has been dug a hole with a knife in advance and put it on the firewood pile, and then take a pointed wooden stick, and the tip of the wooden stick is against the hole in the wooden board, put on gloves with both hands, and start drilling!

squeak.

squeak.

squeak.

Five minutes later, Xu Jianian was sweating profusely, not even a spark appeared on the board.

The five friends in the same group were very bored, and three of them turned to watch other groups light the fire.

Xu Jianian was equally discouraged, but he still had a second backup method, the convex lens ignition method!

He took out the convex lens and newspaper from the backpack, spread the newspaper on the woodpile, faced the sunlight with the convex lens, focused the light and ignited the fire, the sparks fell on the firewood, and the fire started naturally.

The light is gathered through the convex lens, and a bright spot is created on the newspaper!

This caused an exclamation from the people around them. They stared at the convex lens in Xu Jianian's hand and the light spots on the newspaper with piercing eyes.

Another 5 minutes passed.

The light spot swayed slightly, the newspaper was still a newspaper, and the fire was still off.

The three people who turned back turned to the other side, and also took the attention of the remaining two people by the way.

What's going on, this ignition method is too troublesome!

Xu Jianian angrily took away the convex lens and the newspaper.He looked left and right, and the group members were all looking at other people's fires.So he quickly took out a lighter from his pocket, and quietly poured a little cooking oil on the wood, then rolled up newspapers, ignited them, and threw them into the pile of firewood!

This time, it worked surprisingly well.In a short period of time, the flames rose into the sky, burned the firewood, crackled, and shot straight to the calves of everyone, which was completely different from the other fires with only small fires, and attracted the attention of others, even the teacher, who passed by Every now and then, I have to take a closer look, and especially praise:

"Xu Jianian's team did a good job with the fire."

The affirmation of the authority attracted more attention, admiration and inquiries began to come from all directions, and amidst all kinds of praise, the children were particularly complacent:

Some of the things that are said in books are really troublesome and boring, but there are also some things that are really useful and are the correct inventions of human beings.It seems that to judge the usefulness of a knowledge in the future, I have to try it myself.

After lighting the fire, everyone started cooking.

This is not attractive to Xu Jianian.Averting his gaze, he patrolled the camp, looking for new and interesting gadgets.

The camp is still working hard to light the fire. Not many groups successfully lit the fire. Teachers and campers shuttled among the groups. The campers also used liquid to light the fire, but they used alcohol.

Hmm...alcohol?

Xu Jianian rested his chin.I remembered the content and experiments I had seen about alcohol.In another blink of an eye, he aimed at the small house outside the campsite where things were stored.

When Xu Jianian came outside the small house, an uncle was sitting watching the door. He said, "Uncle, the teacher asked me to get the alcohol for lighting the fire."

Uncle refused to give it to Xu Jianian: "This thing is very dangerous, I can't give it to you, you can ask your teacher to come and get it directly."

Xu Jianian said solemnly: "But our teacher asked me to get it, uncle, why don't I ask the teacher again?"

Uncle nodded: "Go and ask again, maybe you remember wrongly, the teacher asked you to take something else."

Xu Jianian turned his head and ran towards the campsite. He found a female teacher who was closest to the small house.

He had noticed that there was no shelter around him. This distance allowed the guards to clearly see him talking with the female teacher, but he couldn't hear what they were saying at all.

Xu Jianian pointed to the small house and asked the female teacher simply: "Hi teacher, my group doesn't have any clips for holding firewood. Is there a place to get the clips?"

The female teacher glanced at the little house and nodded, "That's right, it's there."

Xu Jianian asked again: "Then can I go directly to get it?"

The female teacher nodded again: "Yes, let's go."

Xu Jianian then ran back to his uncle and said affirmatively, "Uncle, the teacher told me to take alcohol."

The guard uncle has already seen everything clearly.He muttered a few words, probably saying "a little irresponsible", but he turned around and gave Xu Jianian the alcohol for the ignition.

Alas, grown-ups always only see what they think they see.

Xu Jianian calmly took what he wanted, and turned around to do a comparative experiment, but at this moment, he suddenly found a group of sneaky people walking out in the crowd!

Isn't the one at the beginning Sheng Xunshu?

The four of Sheng Xunshu hid the teacher and came to the stream, and then followed the stream all the way down to the pool directly below the camping area, where the stream converged.

The meandering creek is not deep, but the pool below the creek is not shallow, like a small reservoir.There are also several wooden stakes beside the pool, and the edges of fishing nets are tied to the wooden stakes.About ten steps back from the edge of the pool is a broken platform. The broken platform is inclined. The highest point is two meters away from the pool. There are small pieces of trees planted on it. of the situation.

Sheng Xunshu came to this feng shui treasure, impatiently stretched his hands into his bulging pockets, and pulled out the red firecrackers from them.

The rest of the people laughed and pulled out their hands too.

Several people looked at each other, and Sheng Xunshu proudly said to everyone: "Okay, we can fry fish—"

Xu Jianian has caught up!

He got out from the bushes, stood on the high platform and looked down, and said to Sheng Xunshu, "How about I come to play with you too? But I didn't bring firecrackers."

Sheng Xunshu looked back, a little disgusted: "What's so fun about camping, you know there is a reservoir here and you don't bring firecrackers... Forget it." He patted his chest, very grand, "You can play without them My firecrackers, I brought a lot!"

Xu Jianian ran to the place where the platform was lower than the ground and jumped off.

Sheng Xunshu first introduced his friend to Xu Jianian.The three people standing behind him are all boys, a pair of twins who don't look alike at all, and a classmate who is very short: "Bethan, Bei Lei. His name is He Xiaolong." Then he said to these three people Said, "His family lives next door to mine, and his name is Xu Jianian."

The three of them had actually heard Xu Jianian's name before, and said the same sentence: "You are Xu Jianian!"

That other person's child!

Xu Jianian remained calm and composed: "Yes, I am Xu Jianian."

other people's children.

After getting to know each other, Sheng Xunshu, as the leader, stood up and showed everyone, especially Xu Jianian, the skill of frying fish with firecrackers: "Do you have a lighter? I'll teach you how to play it. Look at it, light it up, and hold it for a second. Throw hard—bang!"

He uttered an onomatopoeia, and the lit firecrackers came to the top of the water in response, blasting out a beautiful splash!The splash of water, accompanied by the sound of "sand", is the note of nature falling.

Xu Jianian watched Sheng Xunshu's movements carefully, his heart was about to move, but he was not in a hurry to do it. He didn't hold Sheng Xunshu and handed it to his little half until he observed the specific time required for the firecrackers to explode from ignition to explosion. Firecrackers try.

He threw the first firecracker, and the firecracker was thrown a little harder, and it exploded in mid-air.He threw the second one again. This time, the firecrackers fell into the water a little faster. Although the splashes were blown out, the splashes were not dazzling enough.

Sheng Xunshu was not hesitant to praise: "Yes, yes, you learn very quickly! I never thought you were so good at playing firecrackers."

Xu Jianian threw firecrackers for the third time.This time, neither early nor late, the water splashed like a blue flower blooming on the water.Then the fourth time, the fifth time, the sixth time, and every subsequent time, every water flower that Xu Jianian exploded was the biggest one among the water flowers.

He quickly lost interest in this simple splash game.

He asked Sheng Xunshu: "Isn't this a game of frying fish? Where's the fish?"

Sheng Xunshu: "Because it hasn't exploded yet..."

No, things are not as wrong as they said.

Xu Jianian thought about it.

When he threw the firecrackers just now, he aimed at the fish under the water surface, but several times, even though he had already thrown them beside the fish, he just scared the fish away instead of blowing them up.

This means that the power of a single firecracker is completely unable to fry fish!

So if you want to fry fish, you should—

Xu Jianian's eyes aimed at the whole roll of firecrackers brought by He Xiaolong, and he ran to He Xiaolong's side: "How about we try throwing the whole roll of firecrackers into the water? Maybe it will blow up two meters of water Flowers!"

He Xiaolong was taken aback, and said: "No way, the firecracker fuse will stop ringing if it is soaked in water."

Xu Jianian said: "What's so difficult about it? Just protect the lead wires."

He Xiaolong was persuaded by Xu Jianian. He also wanted to see what the two-meter-high water splash looked like, so he handed over the whole roll of firecrackers to Xu Jianian.

Xu Jianian started immediately.He sneaked back to the campsite first, found a large piece of lard from the campsite, then returned to the edge of the pool, and smeared He Xiaolong's firecrackers with lard.

The rest of the people discovered Xu Jianian's various actions, and Sheng Xunshu came over curiously: "What are you doing?"

Xu Jianian said "shh" mysteriously, and waved his hand to signal everyone to stand against the earth and rocks of the broken platform.Then light the firecrackers that have been waterproofed and throw them forward!

The festive red color draws a parabola in the air, the firecracker touches the water, and after the ups and downs, it explodes!

I saw bright light suddenly appearing in front of my eyes along with the explosion, and a mushroom-like water cloud suddenly appeared in the center of the explosion, and then the mushroom water cloud dissipated, the water surface sank, and the water flowers suddenly flew into the air, among which there were countless people with white bellies fish, here is a small fish farm!

With a heavy "bang", floods fell from the sky.Crackling, there is a rain of fish in the sky!

Amidst the loud noise, the rest of the children were dumbfounded.

Sheng Xunshu opened his mouth wide and asked, "Why wasn't the fire on the firecrackers put out by the water..."

Xu Jianian was also puzzled: "Oil can insulate water, don't you all know? Otherwise, why can't water be used to put out a fire in an oil pan?"

The sound fell, and suddenly there was a loud voice from above, and the adults were shouting loudly:

"what happened?"

"Go down and see!"

They turned their heads at the same time, Xu Jianian's position was the outermost, and he could clearly see that in the camping area, several nearby male teachers ran towards this side. arrive!

The author has something to say:

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For the steel ball roller coaster made by Duibao, the picture is from the Internet, which is almost this kind of rough handmade type =w=