Colorful rosy clouds often appear on the horizon before and after sunrise and sunset in the morning and evening. Sunrise and sunset are caused by the scattering of light by air. When sunlight enters the atmosphere, it will scatter when it meets atmospheric molecules and particles suspended in the atmosphere. These atmospheric molecules and particles themselves do not emit light, but because they scatter sunlight, every atmospheric molecule will form scattered light.
Source: According to Rayleigh scattering law, the light with shorter wavelength such as violet, blue and cyan in the solar spectrum is the easiest to scatter, and the light with longer wavelength is the easiest to scatter.
Red, orange, yellow and other colors have strong light transmission ability. So we see that the bright sky is always blue, while the light above the horizon is only yellow, orange and red with longer wavelengths. After these rays are scattered by air molecules, water vapor and other impurities, the sky there is gorgeous.
Color. As the saying goes, "Don't go out in the morning, travel thousands of miles at dusk", that is to say, the bright red sunrise in the morning indicates that there are many water drops in the atmosphere, indicating that the weather is going to turn rainy. If there is a fiery red or golden sunset glow, it means that there is no cloud in the west, and the sun can penetrate to form a sunset glow, which indicates that the weather will turn fine.
Why is it easier to pull a cart than to push it?
The trolley is easy to use and can be pushed and pulled. The direction of push-pull is the same as the angle of horizontal line. Is it easier to push or pull the cart? Labor-saving, not labor-saving Mainly depends on how much resistance the wheel receives. Because of overcoming the resistance, the car can move forward. Under the same ground conditions, the greater the wheel pressure on the ground, the greater the resistance, and the greater the resistance. On the contrary, the pressure is small, the resistance is small, and it is labor-saving. When pushing the car, the direction of the force points obliquely downward, which has two functions: one component moves forward to overcome the resistance and make the car move at a constant speed; The other component is vertical downward, which increases the pressure of the car on the ground and increases the resistance. When pulling a cart, the direction of the force is inclined upwards, which also produces two components; A forward to overcome resistance; The other is vertical, which reduces the pressure of the car on the ground and reduces the resistance. Therefore, the resistance to be overcome when pulling the cart is small and labor-saving.
Why do people with heavy loads walk like jogging?
When people walk, their left and right feet move forward alternately. If it is right, people's walking can be considered as a substitute for falling. When a person stands still, the vertical line drawn from the center of gravity of the human body is always in the area formed by his feet, which is called a state of balance when standing. When people start to move forward, they always lean forward first, so that the vertical line drawn from the center of gravity of the human body comes out from the bottom, forming a tendency to fall forward. Then immediately put your hind feet forward to maintain a new balance. So when we say step by step, we mean going forward again and again. This tendency to fall forward is related to the weight of the human body and the size of the steps taken. The worse the tendency to fall forward, the heavier the impact on the ground when the foot touches the ground, which not only makes people feel tired, but also makes the footsteps difficult to stabilize. Walking with load is equal to the weight of human body. Taking your hind feet quickly can prevent you from falling. Therefore, people who carry loads always take small and urgent steps, which is called trotting. Also, short steps can speed up even under the condition of load, so that load can advance with people at a constant speed. If the steps are big and slow, the goods will be wobbly and difficult to pick up.
Why is a bottle full of water not easy to break?
There are two identical glass bottles, one is empty, the other is full of water, and at the same time it falls to the ground from the same height. Which bottle breaks easily? Generally speaking, heavy bottles break easily. However, when the bottle is filled with water, the water in the bottle has another function, which can reduce the deformation of the bottle, but make it not easy to break. Most of the broken glass bottles are caused by deformation. When the empty bottle falls to the ground, it exerts pressure on the bottle, which deforms from the outside to the inside and eventually breaks. The bottle is filled with water, which reduces the deformation and is not easy to break.
Have we inhaled the soda?
When we suck soda through a straw, we always think that our mouth sucks it up. Actually, it is not. It only sucks the air in the straw. As for soda, it is the atmosphere that presses it into the mouth. It turns out that after the air in the straw is sucked away, the soda in the tube is reduced by air pressure, while the soda in the bottle (outside the straw) is affected by atmospheric pressure. These two pressures are not equal, and the atmospheric pressure is higher. You will put soda water in your mouth. If the soda bottle is covered with a cork and a glass tube is inserted in the cork, you can't suck the soda in the glass tube at most once or twice. The reason is very simple, because the atmosphere outside the bottle can't enter the soda bottle, and the atmosphere can't enter the soda in your mouth. Can you still drink soda without pulling out the cork? Although it can't be sucked up, can it be blown up? Blowing air into the glass tube is one way. Blowing increases the gas in the bottle and increases the gas pressure in the bottle. When the gas pressure in the bottle increases, the soda will be pressed out of the glass tube. At this time, as long as you don't leave the glass tube, you can drink soda. The more you blow into the bottle, the more the pressure increases, and you can drink soda smoothly. After drinking some soda, the volume of gas in the bottle increases and the pressure decreases.
tyre tread
You must have noticed that there are uneven patterns on rubber tires such as cars and bicycles. The purpose of adding these patterns is to increase the friction between the wheel and the ground and prevent the wheel from slipping on the ground. As early as around 1892, people began to add patterns to tires when manufacturing wheels. At that time, the pattern was very simple. With the increase of vehicle speed and load, the improvement of road surface and the constant change of tire pattern. In order to meet the new requirements, the current tire patterns can be roughly divided into three categories: general type, high field type and combined type. Their geometric shapes are vertical straight line, horizontal straight line, diagonal line, block pattern and mixed pattern, and all kinds of patterns are suitable for different driving occasions. For example, the vertical straight lines and sawtooth patterns common on bus tires are suitable for driving on hard roads and can eliminate noise, also called silent lines. Suitable for high cross-country tread, large and deep, not easy to sink when driving, but can "chew mud" well, so that the wheels do not slip. Tractors and cranes often travel in soft soil, which is especially suitable for using this kind of tread tire. Combined tread tire has strong adaptability, and can be driven on both soft and hard roads, even on ice and snow roads, so it is the most widely used.
Reference:/zhuomouniaojiayuan/blog/item/21e108338728edf81a4cff89.html.
Physical knowledge in folk proverbs
In daily life, we often come into contact with some folk proverbs and aphorisms, which contain rich physical knowledge. If we pay attention to analyzing and understanding some folk proverbs and proverbs, we can deepen and activate our knowledge in real life, which is of great help to cultivate our ability to analyze and solve problems. Here are a few examples:
According to the principle of lever balance, if the power arm is a fraction of the resistance arm, then the power is several times the resistance. If the weight arm of the weight is large, it is entirely possible to "dial one or two kilograms".
2. Broken mirrors cannot be reassembled-when the distance between molecules is large (more than several hundred angstroms), the attraction between molecules is very small, almost zero, so it is difficult to reassemble broken mirrors.
What you can't catch is the flowers in the water that the mirror can't catch-the image of the flat mirror is a virtual image.
If the directions of the components are the same, the resultant force is equal to the sum of the components.
5, hemp rope to lift tofu-can't lift it-when the pressure is constant, if the stress area is small, the pressure will be great.
6. True gold is not afraid of fire, and truth is not afraid of argument-although the melting point of gold is not the highest, it is also 1068℃, while the temperature of general flame is about 800℃. Because the temperature of the flame is lower than the melting point of gold, gold cannot be melted.
7. Lunar halo wind, wet rain on the foundation-when the wind comes, the temperature in the upper air drops rapidly and the water vapor condenses into small drops. These small water droplets are equivalent to many prisms, and the moonlight is scattered through these "prisms" to form a colorful halo, so it is said that "the halo is moist and windy". The wet foundation is the ground against the tide. Before the rainstorm, the air humidity was high, the ground temperature was low and it was close to the ground.
8. With a long whistle, the mountain cries and the valley echoes-people whistle in the mountains, and the sound can form a loud echo after many reflections, which will last for a long time. As if the mountains were shouting and the valleys were echoing.
9, but smell the sound, don't smell people-in the process of wave propagation, when the size of the obstacle is less than the wavelength, obvious diffraction can occur. Generally, the height of the fence is several meters, and the wavelength of sound wave is larger than the height of the fence, so you can enclose the high wall for people outside the wall to hear; The wavelength of light wave is shorter (about 10-6 meters), which is much smaller than the size of a high wall, so the light emitted by people cannot be diffracted outside the wall, and people outside the wall can't see people inside the wall.
10, boiling water doesn't ring, ringing water doesn't open-before the water boils, the bubbles in the water rise and vibrate up and down due to convection, and most of the bubbles burst under the pressure in the water, and their cracking and vibrating sounds produce a * * * sound with the container, so the sound is very loud. After water boils, it is isothermal up and down, and the bubble volume increases. Under the action of buoyancy, it will burst when it reaches the water surface.