-"Today's weather 1 1: 36: 1. The temperature is 23℃ 2. Wind direction 323. Humidity 92% 4. Air pressure 100 1.2 mbar 5. The wind speed is 2 m/s. "
This is the weather in Hefei 1 1: 36 in June. When forecasting the weather, we not only need data such as temperature, humidity, wind direction and wind speed, but also know the air pressure. The weather forecast often says that the air pressure is rising or falling. The increase of air pressure means that the weather will clear up; The drop in air pressure indicates that a storm is coming. So, what is the air pressure? How to measure air pressure? With this question, I'm going to look up information online.
It turns out that air pressure is closely related to air. People used to think that air had no quality. In fact, air is made up of all kinds of gas molecules, and all molecules have mass, so air must also have mass. You see, I also did an experiment to prove it!
This experiment is: blow two balloons of the same size, tie them tightly and fix them at both ends of a balance with tape to keep balance. Then, puncture the balloon on the left with a needle, and you will find that the balance is out of balance and tilted to the right. It can be concluded that the air in the left balloon is reduced, and the right balloon is heavier than the left, so it falls down. Obviously, air has quality. Imagine you go to school with your schoolbag on your back. The schoolbag is heavy and the strap is on your shoulder. When you walk into the classroom and take off your schoolbag, you feel that all the pressure has disappeared, but this is not the case, because the air is of quality and its gravity is still pressing you. The atmospheric pressure per unit area is called atmospheric pressure. Middle school students' science and technology network
How do you measure the air pressure? I wanted to find out the truth, so I asked my father. My father explained, "There is a barometer to measure atmospheric pressure. There are two kinds of barometers: mercury barometer and empty box barometer. Mercury barometer is the earliest invented barometer, which consists of a glass tube with an opening at the bottom and containing mercury. The upper space of mercury in the tube is vacuum, and its open end is placed in a container containing mercury. The pressure is the same as that of the mercury column in the glass tube. At sea level, the height of mercury column is generally 76 cm. The greater the air pressure, the greater the pressure on the surface of mercury, and the higher the mercury column rises; When the air pressure drops, so does the mercury column. There is also a barometer called an empty box: this barometer can be installed on the wall, and there is no liquid in it, but a sealed metal empty box. This metal box is very sensitive to the change of air pressure. When the air pressure rises, the thin wall of the metal box sinks inward; When the air pressure decreases, the thin wall protrudes outward. The metal box is connected with the dial. When its shape changes, the pointer on the dial rotates.
How does the air pressure change? I thought of such a problem again. If 10 books are piled up, which book do you think is the most stressful? Is it the second one above or the one below? The former only needs to bear the gravity on it, and the latter needs to bear the gravity of all the books on it.
Sea level is like a book at the bottom, bearing the greatest atmospheric pressure. The altitude is called altitude. The higher the altitude, the smaller the air pressure. The air near the top of the atmosphere, like the top book, has a lower pressure, so the pressure is lower.
If you stand on the Kunlun Mountain at an altitude of 6000 meters and run for a few steps, you will soon be out of breath. Why is it difficult to breathe at high altitude? It turns out that the higher the altitude, the lower the air density and the lower the air pressure. And oxygen only accounts for 2 1% of the air. With the decrease of oxygen, the amount of oxygen absorbed by the human body is relatively reduced, so you will find it difficult to breathe.
Today I learned the secret of air pressure, which benefited me a lot. hydraulic/water pressure
-I remember washing clothes in the river once. I occasionally put my hand in deep water and suddenly felt an upward force pushing my hand. I thought it was fun, so I made it a few times. Why is water like this? I looked at the water in a daze and asked my mother. My mother said that water has pressure, so I became curious about the pressure of water and wanted to know what determines the pressure. After returning to China, I checked some information on the Internet and learned that the pressure of water is determined by the depth. The deeper the water, the greater the pressure. The shallower the water, the less pressure.
I did an experiment for this. Materials: 1 rectangular carton, 1 washbasin, 1 nail, 1 roll tape.
I put away the rectangular paper box and poked three holes on both sides with nails. The positions of the three holes are respectively the upper part, the bottom part and the middle part. Then seal the three holes with adhesive tape, fill the carton with water, put the flat plate under the perforated side and tear off the adhesive tape. I found a strange phenomenon. The water sprayed at the bottom is the farthest, followed by the water in the middle, and the water sprayed at the top is the closest. Through this experiment, I found that the depth of water is different and the pressure of water is different. The deeper the water, the greater the pressure; The shallower the water, the less pressure.
In order to know what other factors are related to stress. I did another small experiment: I found two sponges with the same size, two identical cups, one filled with water and the other with half a glass of water, and put two cups with different water on the sponge. Do you know what will happen? The sponge under a cup full of water is lower than that under a cup half filled with water. Why is this happening? It turns out that water pressure is also related to weight. The heavier the weight, the greater the water pressure.
Pressure is everywhere, including water pressure and atmospheric pressure, which are closely related to our lives. The pressure is far away and close at hand! Nature is wonderful.