Secrets in the guardrail on the expressway [Source: Science and Technology Network for Middle School Students | Time: 2010-4-215: 47:18] Two days ago, our family went to other places to play. On the way through a long highway, the car sped, feeling very flat and the scenery was beautiful. When we got home, it was already dark. But it was a surprise: I found a little secret hidden in the guardrail. Whenever night falls, the lights of the car turn on and shine forward. The guardrails on both sides of the front of the car are like countless street lamps, arranged evenly, like a string of dazzling pearls, illuminating the whole road brightly. I asked my father curiously why. He only explained roughly that it was due to the reflection of light. This can improve security. In order to find out, I went home and looked up a lot of information. It turns out that there are many reflective plates, reflective lights and reflective signs on the expressway. They can reflect light, because there are glass beads on the reflective coating, which refracts and scatters light. There are signs made of reflective materials at intervals on the expressway, including normal straight sections of 50m and 20m bends 1. The ramp is 5m/ ramp, which has obvious warning function. The surface of this signboard is coated with a fluorescent paint with high reflectivity, which can reflect the light incident from all angles into relatively concentrated parallel light. Without light, it will be very dark. Once the light hits the surface of the signboard, it will be reflected back to its original direction. In addition, as long as the automobile taillights hit these reflectors, they can produce the same luster as fog lamps. Very conspicuous. If the reflector on the expressway is dense, new and big, it will give people a feeling of being suddenly enlightened. Under the action of the reflector, the width, turn and slope of the expressway ahead can be seen at a glance, and drivers can drive easily with a good vision, which reduces the occurrence of many accidents at night. There is still a lot of scientific knowledge on the expressway. I will continue to explore more secrets and solve more problems in the future! The Mystery of Molecular Potential Energy [Source: Middle School Students' Science and Technology Network | Time: 2010-5-21:47:13] Seeing such an experiment in a book, the book says it is a puzzle, but it can actually be explained by existing physical knowledge. Connect it to a bracket of about 1m, and connect it to a cylindrical object at the other end, winding it for 5~6 times. Be careful not to bend the pipeline and keep it open. What is more noteworthy is that the horizontal height of one end of the funnel is greater than the height of the water outlet at the other end, and then water is injected from that end of the funnel. People will find that when the water level at one end of the funnel is very high, it is much higher than the water level at the other end. Water will not flow out from the other end. The experiment was published in a book in the form of a jigsaw puzzle. Everyone found it difficult to explain the experiment. In fact, in this experiment, the air in the spiral pipe is the first thing to pay attention to. If there were no air, this phenomenon would not occur. To explain this experiment, we should start with the knowledge of gas compression. We know that gas compression produces internal energy. Internal energy consists of molecular potential energy and kinetic energy of molecules. Compressed gas reduces the distance between molecules, and the gravity of water in the water pipe does work on the gas. One part is the kinetic energy of molecules, which exchanges energy with the outside world in the form of heat, and the other part exists in the form of molecular potential energy. According to the law of conservation of energy, high-level water cannot pass through the spiral pipe with air, and of course the molecular potential energy of gas is limited. When water with high gravitational potential energy can pass through, molecular potential energy needs energy to recover under natural conditions. If there is no molecular potential energy, the gas will be infinitely compressed without restoring its original volume, which is not in line with the actual phenomenon. This has great application value in industry and life. In order to ensure the pressure of pipeline transportation is enough, the gas in the pipeline must be exhausted. In order to ensure smooth transportation, molecular potential energy is also widely used in automobiles, such as airbags and airbag suspension systems. The airbag plays a recoil role, which is the transformation of compression work and molecular potential energy in a microscopic sense. I once played a game when I was young. In an empty glass bottle, I put a lighted firecracker, and the bottle won't break. In the same glass bottle, I added water and set off a firecracker. Of course, this is very dangerous. I hope you don't imitate. At that time, it was just for fun and I didn't know how it worked. The molecular potential energy of water changes little, while that of gas changes greatly. In another sense, it shows that molecular potential energy plays a buffering role. There are too many unknown human beings in the micro-world, which need you and me to discover. I believe that if you observe phenomena in your life, understand the essence from the phenomena and think about science from the essence, you will surely succeed! Author: Leng Bowen The Relationship between Human or Animal Survival and Plants in Quanzhou High School in Guilin, Guangxi [Source: Middle School Students Science and Technology Network | Time: 2010-4-215:17: 37] A few years ago, our family moved into a new house. Just after we moved home, my uncles and aunts gave us some pots of flowers. Dad smiled and said, "Plants can create an atmosphere and purify the air. No one can live without them and no one can live without them. " There are many uses. Can people or animals live without plants? Why can't people or animals live without plants? I'm skeptical. I decided to do a few small tests to prove this problem and dispel my doubts! On Sunday, I bought two mice from a pet store. These two poor mice will be my experiments. They kept struggling, and their little round eyes kept staring at me. I put the first little mouse in a big fish tank, and then sealed the fish tank tightly for fear that the air in the bottle would communicate with the outside air. I watched carefully and saw the little mouse running forward quickly along the wall of the fish tank and around the bottom of the tank. Hey, little mouse! Isn't it true what dad said? However, within a few minutes, I saw the little mouse circling more and more slowly until it was completely bored and dying. At this time, I took away the plastic wrapped in the fish tank, caught the first mouse, put it on the second mouse, moved it into four pots of leafy plants, and then covered it with plastic. I kept patting the fish tank and saw the little mouse running around in panic. After a long time, I didn't see it die. This experiment really proves that plants can transport the oxygen needed by animals. In order to further prove the dependence of humans and animals on plants, I came to a factory near our hometown. The air there is full of muttering dust smell, which makes me cough. I feel very uncomfortable. Then I ran to a bamboo forest behind our house, which is a place with fresh air. It feels extremely refreshing. Breathing fresh air makes people feel much more comfortable. This experiment proves that plants can purify the air and make people breathe smoothly. So these two experiments are enough to prove that the survival of human beings and animals is closely related to plants. How scientific is this? Out of curiosity, I went to the library to consult many books on science and technology, and also searched online, and summarized the following points: 1 People must rely on plants to provide oxygen, and only plants can make oxygen. If a person lives without eating or drinking for a few days, he may die in a few minutes, and oxygen is the first need of human life activities! An adult breathes about 20,000 times a day, inhaling 0.75 kg of oxygen and exhaling 0.9 kg of carbon dioxide. 2. Breathing of animals and plants and burning of substances will also consume oxygen and release carbon dioxide. In this way, isn't the oxygen in the air increasing day by day? Don't! The reason why this kind of crisis has never happened between heaven and earth is that plants are both "producers" of natural oxygen and "broad markets" of carbon dioxide. 3. According to statistics, the broad-leaved forest of 1 hectare can produce 750 kilograms of oxygen and consume 1 1,000 kilograms of carbon dioxide every day in the growing season. Therefore, as long as there are 654.38+10,000 square meters of trees, it can be done. And absorbs exhaled carbon dioxide. Because there are plants that constantly supplement oxygen, the oxygen in the air can be kept basically constant. On the contrary, without plants, the oxygen on the earth can be used up in about 500 years. Therefore, human beings and animals can sustain life, and the oxygen needed for activities must be attributed to green plants. Plants are closely related to our human and animal lives. Here, I call on people in the whole society to stop cutting down trees. Let's live in green plants forever and enjoy the new life brought by its oxygen release! The consistency of the lack of relativity [Source: Middle School Students' Science and Technology Network | Time: 2010-5-211:48: 37] In life, there are many physical quantities related to time, such as the swing period and specific heat. Why do you need time? Obviously, time is not a kind of. Inertia exists in four-dimensional space (i.e. space-time), and space-time has a qualitative nature (the position is not easy to change), which makes objects have inertia. The simplest proof is the mechanical clock, which works by the inertia of matter. Without inertia, the clock will reach the speed of light. There are many examples, such as LC oscillator circuit, where it takes time for an object to fall. The performance of inertia is not in three-dimensional space. Is the relative relationship with the time dimension. The acceleration of an object does work on a substance in the space-time dimension, while the deceleration means that this substance does work on a moving object. About this substance, we need to prove it and understand its microscopic significance. The work done by inertia in time and space should satisfy w=mav, so in the time dimension, it is necessary to do work to change the time distance, that is, to accelerate the movement, rather than change or do work. That is, moving or standing still at a constant speed. The middle school students' science and technology network can achieve great speed with only one force and no friction. Are the two directly related? We can compare inertia and friction. Friction can convert the kinetic energy of an object into internal energy, while inertia can transfer the kinetic energy of an object to the time dimension, and it can move again without loss. This is the difference between inertia and friction. It takes a lot of effort for a massive object to reach the speed of light. Because inertia constrains the motion of objects, it is not impossible to surpass the speed of light. Milk can be sterilized with instantaneous high temperature and instantaneous high speed, which does not violate the law of conservation of energy. But it cannot travel through time and space. Light is only a manifestation of matter, and it is also produced from matter. Just like the sun we see now is the sun five minutes ago, because only information meets people at the speed of light, even if it can cross, it will not change history. Because it's just information transmitted at the speed of light. It is very dangerous for people to travel through time and space. Any action will change history, but our time and space have never changed, which shows that human beings have never traveled through time and space in a limited time. Maybe the time and space they traveled through is not our one dimension, but a copy of our one dimension. If we can travel through time and space, how did we get here? What is the future? We only know a short part of the time, just like a small part of the movie. Even if there is any power to speed up the movement of time, people will not feel that many things in time and space have been determined, and there is a substance that people don't know that gives people consciousness. We all have this feeling that everything outside our own consciousness is certain, but our own consciousness can change these certain things, and our own consciousness is also certain in the eyes of others. This is a very profound logical relationship. Using this relationship to determine the "relativistic" time movement between people is imperceptible to human consciousness. When people ascend in an elevator at an acceleration of 9.8m/s2 in space, the effect is the same as that of people on earth. Inertia is relative to time, and force is a continuous quantity. Inertia is stationary in the time dimension, and motion is acceleration. If time is related to the speed of light, inertia is a manifestation of time, and the more objects move in the time dimension. The lower the ratio to the speed of light, the greater its energy. Inertia comes from the time dimension. Will there be anti-inertia when it exceeds the speed of light? The magnitude of inertia should be proportional to v/c, and this formula can be deduced by adding other quantities. Why do magnets make noise when they are close to recording? [Source: Science and Technology Network for Middle School Students | Time: 20 10-4-2 15:20:05] Every night, I turn on the tape recorder to listen to English words. This Wednesday, my schoolbag was on the table. I turned on the tape recorder to listen to English words as usual. The sound from the tape recorder is not crisp and pleasant, but hoarse and unpleasant! So I asked my father to see if there was anything wrong with the tape recorder. Strangely, there is nothing wrong with the recording and the tape! Is there something wrong with my ears? No, it won't. It must be the recorder! But why is the recording machine noisy? Was it bad before? Why is there noise on the recording machine this day? Dad said, "Did you put a magnet next to the tape recorder?" I suddenly realized that there was a magnet on the schoolbag. Why does the magnet make noise when it is placed next to the tape recorder? I looked up a lot of information about this problem. I found that the tape of the tape recorder is coated with special magnetic powder. When the tape recorder records, it converts sound waves of different intensities into magnetic signals. When we listen to English words, this magnetic signal becomes sound waves. In this way, we can hear the sound recorded on the tape. If the magnetic tape is close to the magnet, the magnetic signal will be attached to the magnetic tape, and the magnetic signal on the magnetic tape will change. We can't believe everything in the data. We have to experiment with our own hands before we can draw a conclusion. The tools of the experiment are: a big magnet, a tape recorder and a good tape. I put the tape in the tape recorder for a few minutes, and then put the magnet next to the tape recorder for another few minutes. You will find that the magnet is really noisy next to the tape recorder. The closer you get, the louder the noise. When you get close, the sound in the tape recorder becomes very strange, so funny! When you remove the magnet, the sound of the recorder returns to normal. I found the secret! Content reprinted from middle school students' science and technology network