China Naming Network - Eight-character Q&A - Fourth grade scientific common sense handwritten newspaper

Fourth grade scientific common sense handwritten newspaper

1. Common sense of science homework in grade four

Fourth grade science common sense homework 1. Little knowledge of science in grade four (I)

Simple and easy-to-learn scientific knowledge

The mystery of automatic rotation

Thinking: Why do cartons full of water rotate?

Materials: empty milk box, nails, 60 cm long rope, sink, water.

Operation:

1. Punch five holes in the empty milk box with nails.

2. One hole is in the middle of the top of the carton, and the other four holes are in the lower left corner of the four sides of the carton.

3. Tie a rope about 60 cm long on the top hole.

4, put the carton on the plate, open the carton mouth, quickly fill the carton with water.

5. Lift the rope at the top of the carton by hand, and the carton rotates clockwise.

Description: the water flow produces equal and opposite forces, and all four corners of the carton are pushed by this force. As this force acts on the lower left corner of each side, the carton rotates clockwise.

Create:

1. If a hole is punched in the center of each side, how will the carton rotate?

2. If the hole is located in the lower right corner of each side, which direction will the carton rotate?

Boat and paddle

Thinking: Have you ever seen boating? Rowing by yourself? Do you know why the ship is moving on the water?

Materials: scissors 1, cardboard 1, rubber band 1, washbasin and water 1 basin.

Process:

1. Cut the cardboard into about 12cm * 8cm long.

2. One end of the bow is cut into a sharp shape, and the other end is cut out of the center of the stern by about 5 cm.

3. Cut a piece of cardboard about 3cm * 5cm to make ship pulp.

4. Tie a rubber band at the stern and tie an oar.

5. Turn the cardboard paddle counterclockwise and tighten the rubber band, and the boat will move forward.

6. If you turn the cardboard paddle clockwise to tighten the rubber band, the boat will move backwards.

Description:

1, the rubber band twists in different directions, but the ship's direction is just the opposite.

2. The power of paper boat movement comes from the energy of rubber band torsion.

2. Fourth grade (1) Scientific knowledge

Simple and easy-to-learn scientific knowledge The mystery of automatic rotation: Why do cartons filled with water rotate? Materials: empty milk cartons, nails, 60 cm long rope, sink, water operation: 1. Punch five holes in the empty milk box with nails. 2. One hole is in the middle of the top of the carton, and the other four holes are in the lower left corner of the four sides of the carton. 3. Tie a rope about 60 cm long on the top hole. 4. Put the paper box on the plate, open the paper box mouth and fill the paper box quickly.

Because this force acts on the lower left corner of each side, the carton rotates clockwise: 1. If you punch holes in the center of each side, how will the carton rotate? 2. If the hole is located in the lower right corner of each side, which direction will the carton rotate? Thinking: Have you ever seen boating? Rowing by yourself? Do you know why the ship is moving on the water? Material: 1 scissors, 1 cardboard, 1 rubber band, washbasin and 1 basin water technology: 1. Cut the cardboard about 12 cm *8 cm long. 2. Cut one end into a sharp shape as a bow. Cut a gap of about 5 cm from the center of the other end to make the stern. 3. Cut a piece of cardboard boat pulp about 3 cm *5 cm. 4. Cover the stern with a rubber band and tie it to the oar. 5. Turn the cardboard paddle counterclockwise and tighten the rubber band, and the boat will move forward. 6. If you turn the cardboard paddle clockwise and tighten the rubber band, the boat will move backwards. Description: 1, when the rubber band is twisted in different directions, the ship will travel in the opposite direction. 2. The power of paper boat movement comes from the energy of rubber band torsion.

3. What are the scientific knowledge of the fourth grade?

The first is the "weather" unit.

1. We can describe the weather by the weather characteristics such as cloud cover, rainfall, temperature, wind direction and wind speed.

2. A table that records various weather phenomena every day is called a weather calendar.

3. The function of weather calendar: record and analyze meteorological information, summarize the previous meteorological laws and predict future weather changes.

4. In the weather calendar, the simplified wind speed grades are used to divide the wind speed: 0 is no wind, 1 is a breeze, and 2 is a strong wind.

5. When using a thermometer, it is necessary to wait until the liquid column in the thermometer stops rising or falling before reading.

6. Temperature has a great influence on the weather and is an important record data in the weather calendar. By observing and measuring the temperature of the atmosphere around us, we can know the local temperature. Temperature refers to the outdoor temperature in a cool and ventilated place. The outdoor temperature in a cool and ventilated place can better reflect the local temperature.

7. The law of temperature change in a day is that it rises first and then falls, with the lowest temperature in the morning and evening and the highest temperature at 2 pm.

8. Wind direction refers to the direction in which the wind blows. For example, the north wind blows from north to south. The wind direction can be measured by the wind vane. The direction pointed by the wind vane arrow is the wind direction. If the arrow points to the south, it is the south wind. Wind direction can be described in eight directions: east, south, west, north, southeast, northeast,

Southwest, northwest.

9. Wind speed is calculated by the number of meters per second. An anemometer is an instrument for measuring wind speed. Meteorologists abbreviate wind power as 13. Wind direction and wind speed are also important data in weather observation.

10. Precipitation is the basic feature of weather and also the important data in the weather calendar. Common forms of precipitation are: rain, snow, hail, fog, frost and so on. A rain gauge is a device for measuring rainfall. The unit of precipitation is millimeters. A straight container can be used as a rain gauge. (Remember a book: 13 page precipitation grade table)

1 1. In Qian Qian, the clouds floating in the sky are actually composed of thousands of water droplets or ice crystals, and their shapes are different.

12. According to the amount of clouds, it can be divided into sunny days, cloudy days and cloudy days. (Pictures will be used in this book P 14 to show the cloud cover in various weather.)

13. Meteorologists divide clouds into three categories: cumulus, stratus and cirrus.

4. The more scientific common sense questions, the better.

Scientific common sense exercises 1. The purpose of protecting the environment is (). A. Reduce pollution B. Maintain ecological balance C. Protect animals and plants D. Beautify human living environment 2. "Green Revolution" is all new technological revolutions centered on adopting high-yield and improved crop varieties. It rose in (). A. 1960s B. 1970s C. 1980s D. 1970s Mid-1970s 3. The earliest use of anesthetics in ancient China was in (). A. Bian Que B. Hua Tuo C. Zhang Zhongjing D. Sun Simiao 4. Which of the following is not Edison's invention ()? A. Law of electromagnetic induction B. Look at this matter from a scientific point of view, because (). A. people have emotions. B. The earth revolves around the sun and the moon revolves around the earth. The two rotate at different speeds, resulting in declination, which makes the earth cover a part of the moon. C. the earth revolves around the moon at different inclinations. D. uneven sunshine. 6. In the construction industry of western developed countries, plastic doors and windows are widely used instead of wooden doors and windows. The fundamental reason for this result is () A. Metal doors and windows are expensive; B. Plastic doors and windows have the lowest cost; C. Builders who use plastic doors and windows can enjoy tax reduction and exemption; D. Using plastic doors and windows is beneficial to the protection of non-renewable resources; 7. Pythagorean theorem was first cited in the existing literature in China () A. Nine Chapters of Arithmetic B. Weekly Calculation C. Vertical and Horizontal Diagram D.). The sunshine is too strong. B.antarctica is too cold. C. Because human activities emit a lot of fluorine compounds. There is too much carbon dioxide in the air. Forming the relationship between greenhouse effect and atomic energy and semiconductor, another invention with the same name as computer is (). A. Space shuttle B. Spacecraft C. Optical fiber D. Laser 10. There are two kinds of marking techniques in marine technology: (). A. desalination and offshore fishing B. offshore oil production and desalination C. deep-sea excavation and desalination D. deep-sea excavation and mariculture 1 1. It is generally believed that. The forerunner of these six high technologies is (). A. communication technology B. information technology C. computer technology D. biotechnology 12. The legendary "ghost fire" phenomenon is actually caused by the release of part of reaction energy in the form of light energy during the oxidation of an element in the human body. This element in the human body is (). A. calcium B. iron C. phosphorus D. (). A. blue B. green C. yellow D. red 14. The inventor of the first practical helicopter was (). A. Wright brothers B. Watt C. Sikorsky D. Faraday 15. 1994 In March, the guiding document on the long-term planning of China's economic and social development was (). A. China 2 1 Century Development Agenda B. China 2 1 Century Development Agenda C. China New Century Development and Planning Agenda D. China New Century Development Agenda 16.2 1 Century Science and Technology Pillar will be (). Space technology D. information technology 17. High-tech is the frontier technology of contemporary science and engineering. At present, the recognized technical fields are () A. Six fields B. Eight fields C. Four fields D. Seven fields 18. Environmental protection includes two aspects. They are pollution prevention and (). A. protect rare creatures B. protect nature C. control pollution D. purify air 19. The limit of an ecosystem's self-regulating ability is called (). A. ecological limit B. ecological threshold C. ecological national limit D. extreme ecological value 20. The two iconic technologies of space technology are the space shuttle and (). A. Satellite communication B. Measurement and control. The multiple-choice question for reference answer is1.b2.a3.b4.a5.b6.d7.b8.c9.d10.c12.c13.d65438.

5. 20 words in the fourth grade of scientific common sense

The mystery of automatic rotation

Thinking: Why do cartons full of water rotate?

Materials: empty milk box, nails, 60 cm long rope, sink, water.

Operation:

1. Punch five holes in the empty milk box with nails.

2. One hole is in the middle of the top of the carton, and the other four holes are in the lower left corner of the four sides of the carton.

3. Tie a rope about 60 cm long on the top hole.

4, put the carton on the plate, open the carton mouth, quickly fill the carton with water.

5. Lift the rope at the top of the carton by hand, and the carton rotates clockwise.

Create:

1. If a hole is punched in the center of each side, how will the carton rotate?

2. If the hole is located in the lower right corner of each side, which direction will the carton rotate?

Boat and paddle

Thinking: Have you ever seen boating? Rowing by yourself? Do you know why the ship is moving on the water?

Materials: scissors 1, cardboard 1, rubber band 1, washbasin and water 1 basin.

Process:

1. Cut the cardboard into about 12cm * 8cm long.

2. One end of the bow is cut into a sharp shape, and the other end is cut out of the center of the stern by about 5 cm.

3. Cut a piece of cardboard about 3cm * 5cm to make ship pulp.

4. Tie a rubber band at the stern and tie an oar.

5. Turn the cardboard paddle counterclockwise and tighten the rubber band, and the boat will move forward.

6. If you turn the cardboard paddle clockwise to tighten the rubber band, the boat will move backwards.

Description:

1, the rubber band twists in different directions, but the ship's direction is just the opposite.

2. The power of paper boat movement comes from the energy of rubber band torsion.

6. Scientific knowledge around you. Fourth grade composition, quick, quick, quick.

1. When taking medicine, don't use tea to deliver medicine, because tea will neutralize the medicine and reduce its medicinal properties.

2。 It is harmful to drink tea when you have a fever, because theophylline contained in tea will raise the temperature of human body, affect and reduce the effect of drugs, thus aggravating the condition. Therefore, it is not advisable to drink tea when you have a fever.

3。 Wearing red clothes can absorb and filter out more ultraviolet rays from the sun, thus reducing the harm of ultraviolet rays to the skin.

4。 Children should not eat sugar on an empty stomach, because it will affect normal metabolic function.

5。 Putting fresh eggs in limewater can keep them fresh, because the carbon dioxide exhaled by eggs reacts with limewater to generate calcium carbonate, which blocks the micropores on the surface of eggs and prevents oxidation and deterioration.

6。 In order to prevent food from being affected with moisture, deterioration or deformation, food bags are often filled with gas carbon dioxide or nitrogen; Or put desiccant in the bag: quicklime and calcium chloride mainly absorb water, and iron mainly absorbs oxygen and water; Or vacuum package.

7。 The gases in swim bladder are mainly carbon dioxide and oxygen.

8。 It's important to add some soda when making steamed bread. In order to neutralize the acid produced during flour fermentation, the carbon dioxide produced can make bread loose and porous.

9。 The residual pesticides in vegetables can be soaked in alkaline substances, which can reduce the medicinal properties of pesticides.

10。 Adding vinegar can remove the astringency of preserved eggs.

1 1。 The odor of refrigerator can be removed by activated carbon, that is, the adsorption of activated carbon is used.

12。 The scale on aluminum pot (mainly calcium carbonate and magnesium hydroxide) can be removed by hydrochloric acid or vinegar.

1, quartz clock hanging on the wall, when the battery runs out and stops, its second hand often stops at the position of "9" on the dial. This is because the second hand is most hindered by the large torque at the "9" position.

2. Sometimes, when tap water flows from the adjacent faucet, it occasionally makes bursts of noise. This is because the water pipe vibrates when the water rushes out of the tap.

3. When taking pictures in front of the TV screen, turn off the camera flash and indoor lighting to make the pictures clearer. Because the reflected light of the flash lamp and the illuminating lamp on the TV screen will interfere with the transmitted light of the TV picture.

At the same temperature, frozen meat thaws faster in water than in air. At the same temperature, hot nails cool faster in water than in air. A cup filled with boiling water cools faster when immersed in water than when immersed in air at the same temperature. All these phenomena show that water has better heat transfer performance than air,

5. When the pot is filled with cold water, the water droplets attached to the outer surface of the pot bottom can only dry out after a long time on the flame, and only when they are dry will they boil. This is because the water droplets, the pot and the water in the pot keep heat conduction, and the temperature is similar. As long as the water in the pot is not boiled, the water droplets will not boil, but will evaporate on the flame and gradually dry up.

6. Distorted mirror, the farther people are from the mirror, the more distorted they are. Because the image in the mirror is formed by the reflection of the silver-plated surface behind the mirror, uneven silver-plated surface or uneven glass thickness will lead to aliasing. The farther away from the deformed mirror, the more the reflected light on the silver-plated surface deviates from the normal position according to the principle of light amplification, and the more deformed the mirror is.

7. There are several small holes communicating with the outside world on the side of the gas nozzle of the natural gas furnace, but natural gas will not be ejected from the side holes, but only from the nozzle. This is because the air velocity at the nozzle is high, and according to the principle of fluid mechanics, the air surface pressure is lower than the atmospheric pressure outside the side hole, so the natural gas will not be ejected from the side hole of the nozzle.

8. After blowing the balloon, hold the mouthpiece with your hand and then suddenly release it. The air in the balloon is ejected and the balloon moves due to recoil. You can see that the route of balloon movement is tortuous. There are two reasons: first, the thickness and tension of the inflated balloon are uneven everywhere, which makes the balloon contract unevenly and swing around when it is deflated, thus the movement direction changes constantly; Second, the shape of the balloon is constantly changing during the contraction, so the air velocity on the surface of the balloon is also constantly changing during the movement. According to the principle of fluid mechanics, the air pressure on the surface of the balloon is constantly changing, so the balloon swings and the direction of movement is also constantly changing.

9. When the ceiling fan rotates normally, the tension at the suspension point is smaller than when it does not rotate. The greater the rotational speed, the more the tension decreases. This is because when the ceiling fan rotates, the air has an upward reaction force on the ceiling fan blades. The greater the speed, the greater the reaction.

10, electric furnace "combustion" is the conversion of electric energy into internal energy. Without oxygen, it can only oxidize electric furnace wires, shortening service life.

1 1. Even if there is no wind, the path of paper dropping is tortuous. This is because each part of the paper has different convexity and concavity and shape, so in the process of falling, the air speed on its surface is different. According to the principle of fluid mechanics, there is uneven air force everywhere on the paper, which changes with the movement of the paper, so the paper keeps rolling and falling zigzag.

7. Articles about scientific knowledge

Scientific knowledge: In order to raise body temperature, larger bees always like to stay on some flowers with higher temperature. Bees can find warmer flowers by identifying their colors. This is a new discovery by British researchers. According to a recent report in Indonesia's Compass, people used to think that bees like to choose flowers with more nectar and pollen. This new discovery by British researchers shows that bees need to stay on flowers with high surface temperature to raise their body temperature, which does not need to consume the heat of bees. "The principle is just like drinking a cup of hot water or cold water," said researchers from Queen Mary's College, Cambridge University, UK. Lars believes that if the ambient temperature is too low, the body will consume the energy brought by hot water instead of using the energy stored by the body. He said that if the ambient temperature is too low, bees need to raise their body temperature to about 30 degrees Celsius to fly and stay on flowers with high surface temperature, so they can raise their body temperature without consuming body energy. In order to verify whether bees can judge the surface temperature of flowers by identifying their colors, the researchers used artificial flowers to experiment with a big bee named BOMBUS TERRESTRIS. In the laboratory, the researchers put four artificial flowers in purple and four artificial flowers in pink. In the first experiment, purple flowers were smeared with high-temperature nectar, and 58% of bees stayed on purple flowers. In the second experiment, pink flowers were coated with high-temperature nectar, and about 62% bees stayed on it. Lars said: "If we don't give bees a hint about the flower color of high-temperature nectar, bees will definitely make the wrong choice. The color of the flower can be seen. Bees with higher temperature nectar will think that the surface temperature of this color is higher after seeing the color of the flower. " Researchers believe that this is a form of evolution, and flowers and bees have formed a mutually beneficial relationship. Lars said that about 80% of flowers have a conical surface cell structure. At present, scientists don't know the function of this cell structure, but Lars thinks it is an evolutionary form.

8. Grade Four-Science-Electricity Knowledge

It is found that in ancient times, in China, the ancients thought that the phenomenon of electricity was caused by the excitation of Yin and Yang, and Shuo Wen Jie Zi said that "electricity, Yin and Yang excite brilliance, and it is from rain to charity".

"Vocabulary" includes "thunder from behind, electricity from application. Yin and yang become thin and become thunder, and discharge becomes electricity. "

There is a record about static electricity in Lun Heng (about the first century AD, that is, the Eastern Han Dynasty). When amber or tortoise shell is rubbed, it can attract light and small objects, and it also describes the phenomenon that silk is rubbed to generate electricity. However, ancient China didn't know much about electricity. Around 600 BC, the Greek philosopher Thales (640-546 BC) knew that the friction of amber would attract fluff or sawdust, which is called static electricity.

Electricity in English means "amber" in ancient Greek. Elektron's Modern Exploration in Greece18th century, the West began to explore various phenomena of electricity.

American scientist Benjamin Franklin (1706 ~ 1790) thinks that electricity is a weightless fluid and exists in all objects. When an object gets more electricity than normal, it is called positively charged; If it is less than a positive constant, it is called negative charge. The so-called "discharge" is the process from positive current to negative charge (artificially specified). This theory is not entirely correct, but the names positive charge and negative charge have been preserved.

The concept of "electricity" in this period is a material proposition. Franklin did many experiments and put forward the concept of current for the first time. 1752, in a kite experiment, he put a kite with a key in the cloud with a metal wire, and the metal wire wet by rain led lightning in the air between his finger and the key, which proved that lightning in the air and electricity on the ground are the same thing.

From matter to electric field, electricity began to develop in18th century. 1767 J.B.Priestley and C. A. Coulomb (1736-1806) discovered the law that the force between electrostatic charges is inversely proportional to the distance. /kloc-in 0/800, Italian Volt (A.Voult) made the first battery by immersing copper and tin in salt water and connecting wires. It provided the first continuous power supply and was called the ancestor of modern batteries.

183 1 year, M. Faraday of Britain demonstrated the generation of induced current by using the change of magnetic field effect. In 185 1, he put forward the concept of physical power line.

This is the first time to emphasize the concept of charge transfer to electric field. Electric field and magnetic field 1865, Maxwell put forward the mathematical formula of electromagnetic field theory and provided the concept of displacement current. The change of magnetic field can produce electric field, and the change of electric field can produce magnetic field.

Maxwell predicted the existence of electromagnetic radiation, and such electromagnetic waves were shown in H.Hertz of 1887. As a result, Maxwell integrated electricity and magnetism into a theory, which also proved that light is an electromagnetic wave.

The development of Maxwell's electromagnetic theory also explains the microscopic phenomenon, pointing out that the charge is split rather than continuous. 1895, H.A. Lorenz assumed that these split charges are electrons, and the role of electrons depends on the electromagnetic field of Maxwell's electromagnetic equation. 1897, J.J.Thomson of Britain confirmed that the electronicity of these electrons is negatively charged.

1898, W.Wien observed the deflection of anode rays and found the existence of positively charged particles. The great influence of electricity on human life. The discovery and application of electricity greatly saved human physical and mental work, made human strength grow wings and extended human information tentacles.

The influence of electricity on human life has two aspects: the acquisition, conversion and transmission of energy and the basis of electronic information technology. Discharge is to make a charged object uncharged.

Discharge: discharge does not destroy the charge, but causes the transfer of the charge, and the positive and negative charges cancel each other, making the object abnormal. Lightning: The surface of our earth is covered with a thick atmosphere. Under the irradiation of sunlight, the earth's atmosphere forms atmospheric convection, and some atmospheres contain a lot of water vapor, forming water vapor clouds.

High-speed convective water vapor clouds cut the earth's geomagnetic field, so the water vapor clouds are influenced by the earth's magnetic field, forming huge water vapor clouds with positive and negative charges at both ends of the water vapor clouds. Due to the influence of atmospheric convection, different water vapor clouds meet in the air, resulting in a huge charge discharge phenomenon, forming a spectacular and somewhat daunting natural phenomenon, accompanied by lightning and thunder. Lightning usually occurs in the vigorous rainy season, accompanied by strong winds and heavy rains, and sometimes accompanied by hail and tornadoes.

The natural condition of lightning is that tropical atmospheric clouds move eastward or westward at high speed, which can produce lightning phenomenon. The atmospheric clouds in the cold zone move at high speed, so it is impossible to produce lightning; It is also impossible for atmospheric clouds moving south or north at high speed to produce lightning.

The physical condition of lightning is: 1. The atmosphere that produces lightning is a water vapor cloud composed of aqueous solution and aerosol with water as solvent and other trace substances dissolved in water as solute, and the insulating air around the water vapor cloud. In the mixture of water solution and aerosol in water vapor cloud, there are trace substances such as acid, alkali and salt, which produce freely movable positive and negative ions in water vapor, and these positive and negative ions provide a large number of charge sources for lightning.

2. Driven by the huge airflow, the water vapor cloud needs to cut the earth's magnetic field, so a large number of free positive and negative ions in the water vapor cloud gather at both ends of the water vapor cloud under the action of the earth's magnetic field, forming a huge charge body. Driven by the huge airflow, the water vapor cloud may move upward, downward, eastward, westward, northward and southward. Only when the water vapor cloud moves up, down, east and west at high speed will the high-speed water vapor cloud cut the earth's magnetic field, and a large number of free positive ions and negative ions in the water vapor cloud will gather at both ends of the water vapor cloud under the action of the earth's magnetic field. When the huge water vapor cloud cuts at high speed,

9. The scientific knowledge around you is fast, fast, fast, fast.

1. When taking medicine, don't use tea to deliver medicine, because tea will neutralize the medicine and reduce its medicinal properties.

3。 Wearing red clothes can absorb and filter out more ultraviolet rays from the sun, thus reducing the harm of ultraviolet rays to the skin.

4。 Children should not eat sugar on an empty stomach, because it will affect normal metabolic function.

Putting fresh eggs in limewater can keep them fresh, because the carbon dioxide exhaled by eggs reacts with limewater to generate calcium carbonate, which blocks the micropores on the surface of eggs and prevents oxidation and deterioration. 6。

In order to prevent food from being affected with moisture, deterioration or deformation, food bags are often filled with gas carbon dioxide or nitrogen; Or put desiccant in the bag: quicklime and calcium chloride mainly absorb water, and iron mainly absorbs oxygen and water; Or vacuum package. 7。

The gases in the swim bladder are carbon dioxide and oxygen. It's important to add some soda when making steamed bread. In order to neutralize the acid produced during flour fermentation, the carbon dioxide produced can make bread loose and porous.

9。 The residual pesticides in vegetables can be soaked in alkaline substances, which can reduce the medicinal properties of pesticides 10.

1 1 Adding vinegar can remove the astringency of preserved eggs. The odor of refrigerator can be removed by activated carbon, that is, the adsorption of activated carbon is used.

12。 The scale on the aluminum pot (mainly calcium carbonate and magnesium hydroxide) can be removed with hydrochloric acid or vinegar, and the quartz clock hanging on the wall can also be removed. When the battery is exhausted and stops moving, its second hand often stops at the position of "9" on the dial.

This is because the second hand is most hindered by the large torque at the "9" position. 2. Sometimes, when tap water flows from the adjacent faucet, it occasionally makes bursts of noise.

This is because the water pipe vibrates when the water rushes out of the tap. 3. When shooting TV pictures, turn off the camera flash and indoor lighting, so that the pictures taken are clearer. Because the reflected light of flashlight and floodlight on TV screen will interfere with the transmitted light of TV picture. At the same temperature, frozen meat thaws faster in water than in air.

At the same temperature, hot nails cool faster in water than in air. A cup filled with boiling water cools faster when immersed in water than when immersed in air at the same temperature.

All these phenomena show that water has better heat transfer than air. When there is cold water in the pot, the water droplets attached to the outer surface of the pot bottom can only dry on the flame for a long time, and then they will boil. This is because the water droplets, the pot and the water in the pot keep heat conduction, and the temperature is similar. As long as the water in the pot is not boiled, the water droplets will not boil, but will evaporate on the flame and gradually dry up. 6. Deformed mirrors. The farther the deformed mirror is from the mirror, the more the reflected light on the silver-plated surface deviates from the normal position according to the principle of light amplification, and the more deformed the mirror is. 7. There are several small holes on the side of the gas nozzle of the natural gas furnace, but natural gas will not be ejected from the small holes on the side, but only from the nozzle. This is because the air velocity at the nozzle is high, and according to the principle of fluid mechanics, the air surface pressure is lower than the atmospheric pressure outside the hole.

There are two reasons: first, the thickness and tension of the inflated balloon are uneven everywhere, which makes the balloon contract unevenly and swing around when it is deflated, thus the movement direction changes constantly; Second, the shape of the balloon is constantly changing during the contraction, so the air velocity on the surface of the balloon is also constantly changing during the movement. According to the principle of fluid mechanics, the air pressure on the surface of the balloon is constantly changing, so the balloon swings and the direction of movement is also constantly changing. 9. When the ceiling fan rotates normally, the tension at the suspension point is smaller than when it does not rotate. The greater the rotational speed, the more the tension decreases. This is because when the ceiling fan rotates, the air has an upward reaction to the ceiling fan blades. The greater the speed, the greater the reaction force. The "combustion" of electric furnace is the conversion of electric energy into internal energy without oxygen. Oxygen can only oxidize wires and shorten their service life.

上篇: Orientation Determination of Four Spirits (How to Determine the Position of Qinglong White Tiger) 下篇: The weather is very hot.