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Paper hard sealing shell
Physical physics in life is a natural subject with a long history. As an important branch of natural science, physical science not only plays an important role in promoting the progress of material civilization and deepening human understanding of nature, but also has an indispensable influence on the development of human thinking. From natural philosophy in Aristotle's time to classical mechanics in Newton's time, and then to relativity and quantum mechanics in modern physics, all these are tangible manifestations of physicists' scientific quality, scientific spirit and scientific thinking. With the development of science and technology and the progress of society, physics has penetrated into all fields of human life. For example, just looking for the optical knowledge in the car has the following points: 1. The rearview mirror outside the driver's cab is a convex mirror. Using the divergent function of convex mirror to light, as well as the characteristics of upright, narrow and virtual image, you can see a smaller object and have a wider observation range, thus ensuring driving safety. 2. The reflector in car headlights is concave mirror, which is made by using the property that concave mirror can reflect the light from the light source placed at its focus into parallel light. Car headlights is always equipped with glass lampshades with horizontal stripes and vertical stripes. Car headlights consists of a light bulb, a reflector and a front glass cover. According to the knowledge of lens and prism, car headlights glass cover is equivalent to the combination of lens and prism. When driving at night, drivers should not only see the road ahead, but also see the fixers, road signs, forks and so on. The lens and prism refract the light, so the lampshade diffuses the light to the required direction according to the actual needs, so that the light illuminates the road in front of the car and the roadside scenery evenly and softly. At the same time, this astigmatism lampshade can slightly refract some light to illuminate road signs and milestones, thus ensuring driving safety. 4. After the car is fitted with brown glass, it is difficult for pedestrians to see the faces of people in the car clearly. The brown glass can reflect part of the light and absorb part, so the light penetrating into the car is very weak. In order to see the passenger's face clearly, it is necessary to reflect enough light from the face and transmit it to the outside of the glass. Because the light inside the car is weak and there is not enough light to transmit, it is difficult to see the passenger's face clearly. Except for buses, the front windows of most cars are inclined. When the front window of the car is tilted, the image of the passenger in the car reflected by the glass is in front of us, but the pedestrians on the road can't appear in the air above, so that the image of the passenger in the car is separated from the pedestrians on the road, and the driver will not have an illusion. The front window of a bus is much higher than that of a car. Even the vertically installed front window looks the same height as the window, and pedestrians on the road cannot appear at this height, so drivers will not confuse the image of passengers outside the window with pedestrians on the road. Life is full of physics, and our food, clothing, housing and transportation are all related to physics. 1. Cooking in an electric cooker, cooking in an electric wok and boiling in an electric kettle all use electric energy to convert into internal energy, and all use heat transfer to cook, cook and boil water. 2. The exhaust fan (range hood) converts electric energy into mechanical energy, and air is converted by air convection. 3. Insert the three-pin plug of the rice cooker, electric frying pan and electric kettle into three hole socket to prevent electric leakage and electric shock. 4. The microwave oven has the advantages of uniform heating, high thermal efficiency, sanitation and no pollution. The heating principle is to convert electric energy into electromagnetic energy, and then convert electromagnetic energy into internal energy. The electric light in the kitchen works by the thermal effect of current, which converts electric energy into internal energy and light energy. 6. Kitchen stoves (honeycomb coal stoves, liquefied gas stoves, coal stoves, wood stoves) convert chemical energy into internal energy, that is, fuel combustion releases heat. Another example is as follows: spiced tea eggs are very popular with people, especially when they are hot. Careful people will find that when the eggs are just taken out of the boiling gravy, if they are eager to shell and eat them, it is inevitable to peel them off with the "meat". To solve this problem, there is a trick, that is, soak the eggs just out of the pot in cold water for a while, and then peel them, so that the eggshells can be peeled easily. General substances have the characteristics of expanding when heated and contracting when cooled. However, when different substances are heated or cooled, the speed and amplitude of expansion and contraction are different. Generally speaking, substances with low density are easier to expand and contract than substances with high density, and substances with fast heat transfer are easier to expand and contract than substances with slow heat transfer. An egg consists of a hard shell, a soft protein and a yolk, and their expansion and contraction are different. When the temperature changes slightly or slowly and evenly, nothing can be displayed; Once the temperature changes dramatically, the expansion and contraction speeds of eggshells and protein are inconsistent. When the boiled egg is immediately immersed in cold water, the temperature of the eggshell will decrease and shrink rapidly, while protein is still at its original temperature and does not shrink. At this time, a small part of protein will be squeezed into the short position of the egg by the eggshell. Then, due to the decrease of temperature, protein gradually contracted. By this time, the contraction of the eggshell was already very slow, and protein was separated from the eggshell. Therefore, when peeling, the shell and the "meat" will not come off together. It is very useful for us to understand this truth. If all things that need to undergo great temperature changes are made of two different materials together, their thermal expansion performance must be considered when selecting materials, and the closer they are, the better. Reinforced concrete is widely used when engineers design houses and bridges. Because the expansion degree of steel bars and concrete is similar. Although the temperature is different in spring, summer, autumn and winter, it will not produce harmful forces, so reinforced concrete buildings are very strong. There are countless examples of this. Physics is a practical science, which is closely related to industrial and agricultural production and daily life. Physical laws themselves are generalizations and abstractions of natural phenomena. Physics exists around physicists. Galileo, an observant Italian physicist, took great interest in the swing of the copper chandelier hanging in the air in Pisa Cathedral when he was attending church. Later, after repeated observation and research, he invented the synchronization of the pendulum. In order to understand the essence of "God's wrath", Franklin, an American physicist who is brave in practice, risked his life to bring "God's fire" to the world with an ordinary kite on a day of lightning, thunder and rain, and invented the lightning rod. British innovation scientist Henry? Achar went to the post office to handle affairs. At that time, a foreigner next to me took out a large edition of new stamps to cut and post on the envelope, but he didn't have a knife. I borrowed it from Aga, and Aga didn't have it. The foreigner had a brainwave, took off the pin on the suit and tie, neatly pierced a circle of holes around the stamp, and then neatly tore it off. When the outsiders left, they left Aga with a series of profound thoughts, and therefore invented the stamp punching machine, and the stamps with tooth patterns were born. Archimedes discovered Archimedes principle in ancient Greece; German physicist roentgen discovered x-rays; ..... There are countless examples of physicists who have made great achievements in studying trivial matters around them. Physics also exists around us. After learning the basic knowledge of measurement, we have begun to make a soft ruler. A classmate is ingenious, wrapping the kraft paper soft ruler with transparent glue, which is more firm. Then a box wrapped in bubble gum is used as the shell of the soft ruler, the center of the box is made of iron wire, and the end of the soft ruler is fixed on the shaft, thus a tape measure that can be cleaned and reused is born. At the same time, inspired by the soft ruler, this student solved an exercise through experiments: when measuring the length of an object with a soft ruler, if the soft ruler is lengthened, is the measured value too large or too small? He did such a simulation experiment: draw a straight line on a white paper, mark it with a scale, then stick it with transparent glue, and then pull it down to make a "soft ruler". With the "soft ruler", he not only found the answer to the above questions, but also clearly saw that the graduation value became larger, and he knew why. After learning the knowledge of electricity, the students explored the maximum voltage that the earthworm can bear: when a voltage of 1.5V is applied to it, the earthworm quickly secretes mucus and struggles to jump out of the bottle. Earthworms are electrically divided into two parts when a voltage of 3V is applied. When measuring the power of "2.4V, 0.5A" small bulb and studying its luminous situation, some students are not satisfied with adding 2.4V voltage to the bulb, but do destructive experiments with their own small bulbs, constantly increasing the voltage at both ends of the bulb until the voltage reaches 9V, and the filament of the bulb burns out. When some students are learning the knowledge of evaporation, they take pains to sit at the table and observe the same two drops of water (one of which is flat), and then observe them carefully, and then analyze and compare them to get the factors that affect evaporation; ..... It is not uncommon for students to capture trivial things around them and explore. Things around us are inexhaustible, and they are always used by physics disciplines closely related to real life. Explaining and summarizing the laws of physics with examples around you sounds familiar and easy to accept. As long as we always pay attention to and summarize, we will constantly find something beneficial to physics teaching, enrich our study life, enliven the learning atmosphere and simplify concepts and laws. Today, all the amazing scientific and technological achievements of mankind, such as sheep cloning, internet, nuclear power plants, aviation technology and so on. All of them are based on the observation and research of trivial things around scientists in the early years. In learning, students should establish scientific consciousness, focus on the big picture, start with small things, experience observation, thinking, practice, innovation and other activities, gradually master scientific learning methods and train scientific thinking methods, and soon you will have the mind of a scientist, laying a solid foundation for your amazing development and beautiful life in the future. In daily life and production, we can improve our ability to observe, analyze and solve physical problems by carefully observing the physical phenomena around us and connecting with the physical knowledge we have learned. As a hot subject, physics has numerous applications in life, and the application of physical knowledge in the kitchen is really the tip of the iceberg. We must study harder, accumulate physical knowledge, improve our scientific and technological level and make our life better.