Introduction:
Recently, a toy called "water sprite" appeared in the street, especially in the toy stalls around the school. Because of the bright colors, it really attracted the attention of many students. Many people can't resist the boasting of vendors and often buy a few to take home. At the beginning of school, many students in our class also joined the ranks of buying water sprite. What is water sprite? What is it made of? Harmless to human body. With these questions, I launched a survey of water sprite.
I. water sprite's Analysis
At the end of September, I interviewed the businesses around the school for the first time, and wanted to know where these water sprite came from, whether there were any manufacturers, and whether they met the national health standards, but the businesses around the school avoided answering, and some even threatened us. I had to change my strategy and conduct a secret investigation. I bought a pack first, and immediately dissected water sprite with a knife. Immediately stopped by a vendor: "These are all living things. If you keep touching them, you will kill them. " According to it, this is a kind of artificially cultivated mushroom-like submarine fungus, which is soft, non-toxic and pollution-free. Touching with your hands feels like jelly. Cut it from the middle with a knife, and a transparent liquid flows out. By feeling, I think it is a substance similar to gelatin, which is the main material for making jelly. These water sprite are red, yellow, green, blue, transparent and colorful. They are very beautiful. Round, about the size of soybeans, about 0.5 cm in diameter, soft to pinch, elastic and sticky. A pungent smell makes people dizzy.
After preliminary observation, we think this is a kind of children's toy that is rarely seen. But why does it have so many colors, why does it smell so pungent, and what is its composition? I started the second step; Start recording;
Day 1 day: began to swell. I dropped a drop of ink into the water, and soon the water became clear again. I wonder, is water sprite a sewage cleaner?
On the 2nd-3rd day, water sprite grew a tail. At the same time, it began to decolorize, and its tail was very short, like that of a tadpole.
Day 4-5: Grow wings. (It hasn't grown)
Day 6: Laying eggs. Water sprite's ball is particularly round, can be crushed and has a smooth surface. It doesn't seem to move. After crushing, the inside looks like broken glass, and the inside and outside are transparent. We doubt whether it is still alive, but we will lay eggs again. And very elastic. That's weird.
Second, the composition of water sprite
The whole growth process of water sprite is like a process of cell division. Later, I learned that water sprite is a kind of water-absorbent resin (chemical substance), which is usually made of starch mixed with acrylonitrile or acrylate. They are transparent balls the size of rubber balls, with three colors of red, yellow and blue, which are very eye-catching. They are packed in small plastic bags or small glass bottles. About 60 balls per bottle, the price is 0.5 yuan. Because they change magically when put into water, there is also a mysterious name-"water sprite". These beads are soft, slippery and wet. After swelling in water, some will bulge out a bag and slowly separate it, so that more and more beads will be produced.
Third, water sprite's harm to human body.
Acrylonitrile and acrylate have certain toxicity, so it is impossible for merchants to use expensive food pigments in their production, and some industrial pigments may be added. Therefore, it is suggested that primary school students should not play with this kind of thing, and wash it quickly if the skin comes into contact with it. Of course, parents should also be very careful not to let children play, so as not to eat by mistake.
Fourth, the damage caused by the water demon.
1, the harm to human body. Acrylonitrile and acrylate have certain toxicity, so it is impossible for merchants to use expensive food pigments in their production, and some industrial pigments may be added. Therefore, primary school students are advised not to play with such things. If it comes into contact with skin, it should be cleaned quickly. Of course, parents should also pay great attention to avoid letting younger children play to avoid eating by mistake.
2. Let students develop the bad habit of abusing pocket money. Some even steal money from their parents and blindly follow suit.
3. If water sprite is brought to school, some students will play with water elves under their desks, and they will not listen carefully and distract their attention, thus affecting our study.
1. Small color projection needle
A magnetic needle is a compass. Compass is one of the four great inventions in China. In the present physics teaching, a small magnetic needle can be used to judge the direction of the magnetic field. However, it is very inconvenient to use magnetic needles sold in the market or investigated and dialed by higher authorities. When the teacher is doing the demonstration experiment of magnetic field direction, the students can't see clearly below, so the teacher has to take the instruments down and show them to the students one by one, which is very time-consuming. What shall we do? After trying their best, the students finally made a simple color projection magnetic needle, which can be used as a compass and projected on the projector, so that the whole class can see the direction of the magnetic field, which provides great convenience for teaching experiments. 、
Simple projection needle has simple structure and common materials. It is made of card pins, pins, plexiglass strips and transparent projection film materials. The manufacturing method is: put two steel needles on the two steel needles respectively, and pay attention to the balance of the two steel needles. Then cut the transparent film into sharp long pieces, stick it on the steel needle with 502, one at each end, pay attention to symmetry, and then paint it red and green respectively. In this way, the upper part of the magnetic needle is completed. Saw the plexiglass strip into a block, then grind it into a round base of the magnetic needle, and iron it in the middle of the round plexiglass. Please note that the pin should be perpendicular to the base. The inner groove of the small snap button is used as the bearing support hole for rotation. Put the bearing on the needle tip, so that the magnetic needle will rotate on the needle tip. The last one is to wipe the S pole of the bar magnet from the middle part of the magnetic needle to the green side, and magnetize the small magnetic needle, that is, the N pole. So that the small magnetic needle is magnetized.
Put the self-made small magnetic needle on the projector, and you can see the direction of each point of the magnetic field at a glance from the curtain.
2. Why can clothes keep people warm?
First of all, you should ask yourself: Can clothes really keep people warm?
You know, it's not leather that keeps people warm. On the contrary, people keep fur coats warm. Right? You know a fur coat is not a stove. "What?" You will ask. "Is that man a stove?" Yes, man is a stove! We already know the food we eat-this is chopping wood, which burns in our bodies. At this time, we didn't see any sparks. We say it is burning only because we feel that there is heat in our body.
This heat needs to be protected. In order to prevent the heat in the house from spreading to the street, we built thick walls, installed double windows in winter, and wrapped blankets on the doors. We wear clothes for the same reason. Instead of letting our body's heat radiate to the indoor air or the street, we keep our clothes warm, which keeps our heat around our bodies. Of course, our clothes also give off heat, but it is much slower than our bodies.
3.[ Scientific Papers] Energy-saving street lamps
The Chinese nation has a fine tradition of thrift, and the people of China have maintained this good style since ancient times. This feature is also reflected in productive labor and daily life. We should always try our best to do everything well in the most economical way. It is because of this good idea that we know how to save energy. The energy problem is of extraordinary significance to a populous country like China. With the development of economy and the large-scale exploitation of resources, the problem of energy shortage has become more prominent, which has greatly affected the modernization of China. Up to now, our country still advocates thrift. In the major construction of Olympic venues, the state put forward the slogan of "running the Olympic Games frugally" according to the actual needs. On the 55th anniversary of the National Day this year, the slogan "Save the National Day" was put forward one after another. Our country is proceeding from the overall situation and achieving the diligent style from the aspect of energy conservation. Saving energy can reduce expenses, promote economic growth and protect the natural environment, which is also a prerequisite for taking the road of "sustainable development" and for our future generations.
At night in the city, there are dense and neat street lamps on both sides of the road, which looks like a dragon flying. Although this is a beautiful scenery, many times the lights of these street lamps are wasted because the road is empty for a large part of the time, especially in areas with underdeveloped economy and transportation. The huge waste of power resources has brought negative effects on the economy of these areas, which is not beneficial, but harmful. Then, is there an automatic control device that is convenient for pedestrians and vehicles to pass at night and saves energy?
Saving energy is actually to reduce energy loss as much as possible. On remote roads, the traffic flow is very small, and turning on street lamps for a long time, whether there are cars, no cars, pedestrians or no pedestrians, will cause great waste of energy. You shouldn't turn on all the road lights even if a car passes by. You should only turn on the street lights within the effective range of the vehicle, otherwise it will cause great losses! So do pedestrians walking on the road. Only turn on the street lamps within the corresponding range for pedestrians to meet the lighting needs. This problem can be compared with the common voice switch now. As long as someone walks in the stairwell and makes a sound, the light will light up when the vibration generated by the sound is transmitted to the voice control switch, and the light will only light up within the pedestrian's walking range and will not light up for a long time. From this, we can know that when vehicles and pedestrians pass on the expressway, don't they exert pressure on the pavement? If there is an inductor that can automatically control the switch under the pressure and control the lights on and off within the corresponding range, the purpose of energy saving will be achieved.
Then this sensor can not be controlled by air vibration generated by sound, but by road vibration generated by the impact and pressure of vehicles and pedestrians on the road. These two kinds of vibrations are different, otherwise it is a mistake, which may be the barking of animals. The noise outside the road will turn on the lights, and it will also fail to achieve the purpose of energy saving. If the noise from vehicles and pedestrians is very small, the lights will not light up? That's useless. It doesn't work at all. The driving of cars and the walking of pedestrians will naturally produce impact and pressure on the ground, which will make the road surface vibrate, so that the road surface vibration can be used to control the opening and closing of street lamps. If there is such a device, it can be installed in the light box of a street lamp, and each device is connected to the road surface with a metal bar. When the road surface is impacted and vibrated by pressure, the corresponding street lamps will light up, and the lights will light up where there are vehicles or pedestrians, and the vibration will stop, and the lights will automatically go out within a certain time limit. This device uses vibration and pressure to control street lamps, which can play a very good role in energy saving. Of course, in order to reduce the number of installed devices, such a device can control multiple street lamps, and multiple devices are connected in parallel in a circuit, that is, one device is installed at intervals, and then these devices are connected to the corresponding street lamps through wires. We might as well name it "vibration sensor" first. Let's first look at the working principle of the "vibration sensor": First, the metal bar is used to sense whether the road surface vibrates. When a car or pedestrian passes a certain road section and exerts pressure on the road surface to generate vibration, the metal bar transmits the vibration to the "vibration sensor", which is stimulated by the vibration and commands several street lamps it controls to turn on the switch. Vehicles and pedestrians continue to pass the next road section, and the "vibration sensor" of the next road section is also stimulated by vibration, which also lights up the corresponding street lamps, and so on. At the same time, the "vibration sensor" on the road section after vehicles and pedestrians passed by turned off the switch because it did not continue to receive the vibration information transmitted to it by the metal strip, so that the corresponding street lamps did not continue to emit light. But this kind of "vibration sensor" requires high sensitivity and can also identify the vibration source. For example, under special circumstances, lightning weather or high-decibel noise generated by factories will make the air vibrate violently, and it will also be transmitted to the "vibration sensor" through metal bars. The "vibration sensor" mistakenly thinks that the vibration comes from the road surface, which makes the street lamp shine. Therefore, we need to use science and technology to study and develop a novel. Huh? Don't say that. Apricot ζ ao is out of danger? Visit? Blow molding? So the sheath is charming? Hey? Scratches? Blow?
Well, as long as this "vibration sensor" is installed on the road with street lights, it doesn't need a lot of manpower to control the power supply, and all the work will be automatically controlled by the machine. We can imagine that there are cars or pedestrians passing by on the road, and the scene of street lamps flashing and going out for the second time is dazzling and overwhelming. Isn't evening a unique and beautiful scenery? At the same time of convenient transportation, the biggest advantage is that it saves energy greatly.
This kind of "vibration sensor" is designed to save energy. I hope this device can be applied to practice and play a great role. While developing the economy, we must not ignore the importance of energy conservation, save energy and take the road of sustainable development, which has become the common sense of mankind.
I helped you choose three compositions. I wonder if it will help you.