1. Volcanic activity is a natural phenomenon that is the result of material activity deep within the earth's crust. The volcanic ejecta accumulates into a cone-shaped hill at the mouth of the channel, which is called a volcanic cone. Among the Cenozoic volcanic cones in China, the Paektu Mountain volcanic cone is the largest, with a base area of ??300km, a relative height difference of 1,600m, and a volcanic lake at the top, the famous Tianchi.
When a volcano erupts violently, the volcanic gases mix with the hot volcanic ash to form a tall mushroom-shaped luminous cloud vertically upward, or form a hot volcanic ash flow that rushes out diagonally and flies close to the ground. The temperature can reach 800°C, and the speed can reach up to 100km per hour. 70% to 80% of volcanic gases are water vapor (for example, when the Panicutin volcano erupted in 1943, 1.8×104t of water was released in just one day).
Volcanic eruptions can cause natural disasters. But after a volcano erupts, plants will grow on the cooled lava, and thick nutrient-rich volcanic ash falls on farmland, making the land more fertile.
Excuse me: Why does the mixture of volcanic gas and hot volcanic ash form tall mushroom-shaped cloud columns vertically upward? Why do volcanic eruptions affect climate? How should we view the disasters caused by volcanic eruptions and the life that emerges after volcanic eruptions.
Because the volcano erupts a mixture of high-temperature, high-pressure volcanic gas and hot volcanic ash, the air around it quickly heats up, expands and rises rapidly, and relies on the huge initial kinetic energy when it erupts. High in the sky and form a mushroom cloud. During the ascent, due to contact with the surrounding low-humidity air, the temperature of the mixture of volcanic gas and volcanic ash gradually drops. After reaching a certain height, when the temperature of the mixture is the same as that of the surrounding gas, the mixture of volcanic gas and volcanic ash moves horizontally. Spread out to form a mushroom top, thus forming a complete mushroom cloud.
When a volcano erupts, a large amount of volcanic gas and ash are ejected high into the sky, and will be spread far away by the wind. These volcanic materials block sunlight and filter out certain wavelengths of light. It causes lower temperatures, darkening days and violent storms (even mud rain) over longer periods of time, sometimes affecting the global climate.
Volcanic eruptions are one of the forms in which the earth's internal motion changes from imbalance to a new equilibrium during the evolution of the universe. Therefore, volcanic eruptions are a natural phenomenon, not the end of the world. Volcanic eruptions, a concentrated release of energy, will undoubtedly cause huge disasters, but it should be noted that volcanic eruptions also breed new vitality. In addition, volcanic eruptions can also promote the study of volcanoes, deepen our understanding of the changes in the movement of materials inside the earth, the laws of volcanic eruptions, and the vitality that arises after volcanic eruptions, which is conducive to strengthening the prediction and prevention of volcanic eruptions and minimizing losses. , rationally develop and utilize the vitality provided by the volcanic eruption, and rebuild their homes.
2. Seismic waves are elastic waves generated by the rupture of rocks at the earthquake source when an earthquake occurs. They can propagate in the interior of the earth and on the surface of the earth. During an earthquake, two types of seismic waves are emitted from the earthquake source at the same time: longitudinal waves and transverse waves. The speed of longitudinal waves is greater than the speed of transverse waves. The direct disaster of earthquakes is caused by fault dislocation during earthquakes and ground vibration caused by seismic waves. Mainly include: ground damage, damage to buildings and structures, damage to mountains and other natural objects, ground light burns, etc. Let’s discuss, when an earthquake occurs:
1. What is the difference between the initial and later perceptions of an observer farther away from the epicenter? Did observers near the epicenter feel this way, and why?
2． What are the causes of building damage caused by earthquakes
1. Because the source of the earthquake is in the strata below the ground, the longitudinal waves in the seismic waves cause the ground to vibrate up and down, and the shear waves make objects on the ground vibrate horizontally. And because longitudinal waves propagate faster than mode waves, observers farther away from the epicenter during an earthquake initially feel up and down, and later feel horizontal shaking. What they then feel are longitudinal and transverse waves. Integrated vibration. Because the longitudinal and transverse waves near the epicenter have not had time to separate, observers there can only feel the combined vibration caused by the longitudinal and transverse waves.
2． There are two aspects of seismic wave impact: vertical and horizontal. Longitudinal waves cause buildings to be impacted vertically, shaking up and down, causing transverse cracks in buildings and foundations; shear waves cause buildings to be impacted horizontally, shaking left and right, causing longitudinal cracks and cracks in buildings. collapse. The vibration of transverse waves is very strong and is an important cause of damage to buildings. Some of the ground near the epicenter will also experience cracks, movement, and settlement. If the foundation of a building happens to be in these locations, the building will suffer greater damage.
3 Why is there no sound on the moon?
Sound is 20 to 20,000 vibrations per second in the air. There is sound on the earth because the vibrating object transmits the vibration to the air, and the air spreads the vibration to form sound. Therefore, there are two necessary conditions for the existence of sound: one is that there must be a sound source, and the other is that there must be a medium to propagate the sound, both of which are indispensable. Vibrations can be produced on the moon, but there is no air on the moon, so the vibrations from the vibration source cannot be transmitted. Of course, no sound can be heard on the moon. It is a very silent world there.
It is not difficult to prove that there is no sound on the moon. We can do this experiment: place an alarm clock in a glass cover with air extraction equipment. When the air in the cover is not extracted, we The ticking sound of the alarm clock can be heard. When the air is gradually extracted, the ticking sound gradually weakens; when the air is very thin, the ticking sound is inaudible. If there is no air to carry the sound, we can't hear it even if the alarm clock keeps ticking.
For sound propagation, conditions on the moon are similar to those inside a glass enclosure with air extracted. So there is vibration on the moon but no sound.
On July 21, 1969, humans landed on the moon for the first time. On the moon, although the two astronauts were very close, they could only communicate by radio.
There are also the manifestations of the three states of water in natural phenomena, such as the formation of snow
About ice, snow, frost, hail and clouds, rain, fog, dew and white The formation of Qi has different explanations in various materials, which are not suitable for junior high school physics teaching. For this reason, I have summarized it as follows:
1. Ice: When the temperature is below 0°C, water will release heat and solidify into ice; water vapor will release heat and condense into a colorless, transparent and hard solid, which is called ice.
2． Snow: When water vapor in high altitude encounters cold air currents of 0°C and below, it will release heat and directly condense into small hexagonal white ice flakes and fall. Call it a snowflake.
3. Frost: On a windless and cloudless night or early morning when the temperature is below 0°C, when the temperature of the ground, vegetation, houses, and surfaces is lower than the temperature of nearby water vapor, the water vapor will release heat and condense on the ground, Many small white ice crystals form on the surface of vegetation and houses, which are called frost.
4. Hail: When the small ice crystals in the clouds rise and fall repeatedly with the violently moving cold air flow, they constantly collide with snowflakes and supercooled water droplets, forming transparent and opaque layers, with alternating layers, diameters ranging from 5 to 50 mm, spherical, and conical shapes. Or irregular-shaped ice cubes. When the updraft cannot support these small ice cubes, they will explosively fall to the ground, which is called hail.
5. White gas: White gas is formed when water vapor condenses into small water droplets suspended in the air when it encounters cold edges. In the summer, when you peel off the popsicle paper, you can see the popsicles emitting white gas. The popsicles will also emit white gas when they are just taken out of the refrigerator. These are The formation of white gas is due to a small amount of ice absorbing heat and melting, cooling the surrounding air. The water vapor in the air around the popsicles is condensed into small water droplets and suspended in the air, thus forming "self-gas". Therefore, "self-gas" is formed by the liquefaction of water vapor
6. Cloud: It is a mixture of small water droplets and small ice crystals. Small water droplets are water vapor in the atmosphere that releases heat when encountering cold air currents above 0°C. Dust condenses into a core and liquefies into a huge number of small water droplets with a small diameter. Small ice crystals are the product of sublimation. These small water droplets or small ice crystals are suspended in the air to form visible aggregates, which are called clouds. Therefore, 'clouds' are the product of water vapor liquefying or subliming under certain conditions.
7. Fog: It is a special situation of clouds. The reasons for their formation are basically the same. The difference is that the fog floats low above the ground. Clouds float in the sky, and the water vapor near the ground or on the river surface releases heat when it encounters cold, and liquefies (the temperature is above 0°C) into countless small water droplets or sublimates (the temperature is below 0°C) into countless small ice crystals. Aggregate, called fog.
8． Rain: Under certain temperature and pressure conditions, small water droplets in clouds gradually increase in size due to the continuous liquefaction of water vapor. When they become too large to be suspended in the air, they will fall to the ground, which is called rain.
9. Dew: is liquid water, the little sister of rain that forms on the ground. On a windless, cloudless night or early morning when the temperature is above 0°C, when the temperature of the stones, vegetation or crops on the ground is lower than the temperature of the nearby water vapor, the water vapor releases heat, liquefies into small water droplets and adheres to them. On the branches and leaves of vegetation, stones and crops, it is called dew. Dew is different from rain. Dew is the liquefaction of water vapor close to the ground, while rain is the phenomenon of water vapor high in the sky liquefying and falling to the ground.
There are many, many more...
4. Question type
"Physics" in labor Topic: The cement floor of the basketball court of Shandan Middle School is paved A large wool carpet used for performing theatrical performances. Now according to the requirements of the program, the wool carpet needs to be moved 2 meters forward. Xiao Wang and several other students pulled up one side of the wool carpet and it took a lot of effort to pull it to the front. Please combine the physics knowledge you have learned to answer the following two questions: (1) What is the main reason why wool carpets are difficult to pull? (2) Please think about it, is there any other way to move the wool carpet? (Without the help of equipment, design two simple and feasible solutions, which can be explained with text or diagrams) Answer: (1) The friction between the wool carpet and the cement floor is too great; (2) Roll up the wool carpet and then roll or lift the wool carpet away one side of the destination and make it move forward in waves until it reaches the destination. "Physics" in folk proverbs Topic: There is a folk saying in my country that "if a water tank wears a skirt, it will rain." "Wearing a skirt" in a water tank means that a layer of evenly distributed small water droplets appears on the outer surface of the water tank, downwards from where the water surface is. Regarding the reason for the appearance of small water droplets, which of the following statements is correct ( ).
(A) It is the evaporation phenomenon of water (B) It is the liquefaction phenomenon of water vapor (C) It is the diffusion phenomenon of water molecules (D) There is a crack in the water tank, and water seeps out Answer: B "Physics" in disasters To prevent forest fires, transparent beverage bottles are not allowed to be discarded anywhere in the forest. This is because the effect of rainwater on light after entering the beverage bottle is equivalent to a _________ mirror, and its _________ effect on sunlight may cause forest fires. . Answer: Convergence Convergence As shown in the picture, on a thunderstorm day, a villager went to take shelter under a big tree. Unfortunately, he was hit by a thunderstorm and was seriously injured. After that, rumors spread in the village about being "haunted by demons" and "not practicing well in previous lives"... The family could not hold their heads high in front of everyone. Instead of sending the patient to the hospital for treatment, they instead prayed to God and worshiped Buddha, causing the patient to delay treatment.
(1) Are the views stated in the article correct? Correct point of view? (2) In order to avoid similar accidents, people have installed _________ on tall buildings; (3) If you encounter a thunderstorm, what you should do is _________. Answer: (1) No, thunder and lightning is a natural phenomenon. We must believe in science and get rid of superstition. (2) Lightning rod. (3) Do not take shelter from the rain under big trees or tall buildings. "Physics" in Advertising Title: With the rapid development of our country's economy, many manufacturers have changed their past concept of "the aroma of wine is not afraid of the depth of the alley" and have begun to advertise their products. However, some advertising production has ignored the scientific nature of it. There is a scientific error in each of the two advertisements shown in the picture. Please find it and briefly explain what physical principle or law it violates.
(1) Picture A is wrong: ________, it violates ________; (2) Picture B is wrong: ________, it violates ________. Answer: (1) The water surface of the pot body is lower than the water surface of the spout, but the tea is poured out. Principle of the connector (2) The spoon looks straight. The law of refraction of light. "Physics" in the comics. Question: Please observe carefully the picture. comics. Who gets the heavier carrot, the monkey or the rabbit? Briefly explain the reasons.
Answer: The little monkey received a heavy portion of radish. It can be seen from Figure 1 that when the carrot is balanced, the thick end of the force arm is short. According to the principle of lever balance, it is known that the thick end is heavy. "Physics" in labor One of the wheels of a flatbed truck got stuck in the mud. Xiaohong and Xiaojun came to help. Xiaojun used the method of helping to pull the cart, and Xiaohong used the method of pushing the upper edge of the wheel. If two people exert the same force and the direction is reasonable, the actual effect will be ( ). (A) Xiaojun's is good (B) Xiaohong's is good (C) The same (D) Unable to determine the answer: B "Physics" in cooking The Lantern Festival is a traditional Chinese festival. On this day, the whole family gathers together and often cooks glutinous rice balls to express their gratitude. celebrate. When Yuanyuan helped her grandma cook glutinous rice balls, she discovered that when the raw glutinous rice balls were put into the pot, they would sink due to the buoyancy of ________ gravity (fill in "greater than", "less than" or "equal to"), while the cooked glutinous rice balls would expand due to the heat inside them. , the buoyancy ________ (fill in "increase" and "decrease"), causing the buoyancy to be greater than gravity, and the glutinous rice balls ________.
Answer: Less than, Increase, or Float (Source: Subject Network)