Why don't you drop the paper?

Once, at the end of science class, I heard several students talking in succession. I leaned down and listened carefully. It turns out that everyone is discussing a question: If an empty cup is filled with water, cover it with a piece of paper, and then turn the cup upside down, will the paper fall and the water will flow out? Will such a magical thing happen? I decided to do an experiment by myself.

So when I came home from school, I couldn't wait to find a paper cup, a piece of white paper with the right size, and then filled the cup with water and covered it with paper. At this time, I was a little nervous and worried that the experiment would not succeed. In order to know the result, I took a deep breath, picked up the cup and gently turned it upside down. Wow! If so, the paper is tightly "stuck" to the mouth of the cup, and there is no water leakage. It's amazing!

But why is this? In order to solve the mystery, I searched the internet for relevant information. The air pressure in the original cup filled with water is blocked, and the pressure is naturally small. In addition, the surface of water has expansive force, so that the water in the cup can be "fixed" stably and the paper can be sucked on it.

It suddenly dawned on me that it was air and paper that held the water in the cup!

[Composition of Grade Five] Small Papers on Science and Technology

Eclipse is a special astronomical phenomenon, which means that when the moon moves to the shadow of the earth, the area between the moon and the earth will be blocked by the earth because of the sunlight, and the moon will be missing. That is to say, at this time, the sun, the earth and the moon are exactly or almost on a straight line between the sun and the moon, so the light from the sun to the moon will be blocked by the earth. As far as the earth is concerned, when an eclipse occurs, the directions of the sun and the moon will be different by 180 degrees. Ancient solar eclipse records can sometimes be used to infer the age of historical events. China ancient superstition is also called "dogs eat the moon". Eclipses can be divided into three types: partial eclipse, total eclipse and penumbral eclipse. When the whole moon enters the umbra, a total lunar eclipse will occur; However, if only one department enters the umbra, only a partial solar eclipse will occur. Total lunar eclipse and partial lunar eclipse are umbra eclipses. Composition 600-word composition

During the total lunar eclipse, the moon is not completely invisible, because sunlight is refracted into the umbra when it passes through the weak atmosphere of the earth, and projected onto the surface of the moon, making the surface of the moon appear red copper. According to the path of the moon through the umbra and the atmospheric conditions of the earth at that time, the luminosity will be different in different total lunar eclipses.

Sometimes the moon does not enter the umbra, but only enters the penumbra. This is called a penumbral eclipse. During the penumbral eclipse, the moon will darken slightly, but its edge will not be blocked by the shadow of the earth. But if you want to watch the total lunar eclipse at night, the probability of watching the eclipse will explode? The chances of eating are much less.

There is also a story about the solar eclipse:/kloc-At the beginning of the 6th century, Columbus sailed to Jamaica in South America and had a conflict with the local aborigines. Columbus and his sailors were trapped in a corner, without food and water. The situation is very critical. Knowing that there would be a total lunar eclipse that night, Columbus, who knew something about astronomy, shouted to the natives, "No food, no moonlight!" " In the evening, Columbus's words came true, and there was no moonlight. When the natives saw this scene, they were afraid, so they quickly turned to Columbus for peace.

Scientific paper

With the decrease of energy, people pay more attention to energy conservation. When I was in primary school, my teacher taught us to save energy, so that we human beings could live on the earth forever. In real life, most people still don't know how to save energy, so that saving energy is only something that can be said, but not completely done. Often due to the lack of scientific common sense and "tips", resulting in some unnecessary waste. Now I'm going to introduce some tips for saving electricity at home.

First, the rice cooker power saving tips

There are two kinds of rice cookers on the market now: one is mechanical rice cookers, and the other is computer rice cookers. When using the mechanical rice cooker, cover the rice cooker with a towel, and be careful not to cover the air outlet, which can reduce the heat loss. When the rice soup is boiling, raise the button to dry the rice soup with the waste heat of the electric heating plate, then press the button and stew for 15 minutes. Be sure to unplug the power plug after using the rice cooker, otherwise the temperature in the rice cooker will automatically turn on when it drops below 70 degrees, which will not only consume electricity but also shorten the service life. Try to choose a high-power rice cooker, because cooking the same amount of rice, a 700-watt rice cooker is more time-saving than a 500-watt rice cooker. Computer rice cookers generally have high power, about 800 watts, which is more energy-saving.

Second, TV power saving tips

Television can save energy in the following ways: First, control the contrast and brightness. Generally, the power consumption of the brightest and darkest color TVs can range from 30W to 50W. It is suggested to turn on the low wattage fluorescent lamp indoors and adjust the contrast and brightness of the TV set to the middle. The second is to control the volume, which is loud and consumes high power. In addition, one way to save electricity is to watch DVD, preferably AV status. Because in the AV state, the signal is directly connected, which reduces the work of the TV tuner and naturally reduces the power consumption. Secondly, after watching TV, you can't turn it off with the remote control, but turn off the power on the TV. Because after the remote control is turned off, the TV is still in standby state and still using electricity. Under normal circumstances, the standby time is 10 hour, which is equivalent to consuming half a kilowatt hour. Finally, add a dust cover to the TV set. This can prevent the TV from inhaling dust and increase power consumption.

Third, computer power saving tips

Try to turn off the power switch when not using the computer, which can reduce the power consumption. Cover the computer when it is not in use to prevent dust from entering the computer and reduce power consumption. It is also necessary to take out and clean the motherboard and other components inside the host from time to time, so as to better reduce power consumption! ! Try not to use the computer.

Energy saving is very important. Everyone should use these skills and should not stop doing these things because it is too much trouble. These things are of great benefit to everyone, it's just a little effort. Relevant departments should also increase capacity and publicize more. Let all mankind save energy, which is not always available! Let each of us cheer and work hard for the benefit of future generations!

Model essay on science and technology-pollution-free fly swatter

In summer and autumn, flies often climb on food and chopsticks, which seriously affects food hygiene. People often get sick after eating these foods with bacteria. In order to eliminate flies, flies are often beaten with flies, so that the number of flies at home is gradually reduced. But after hitting flies for a while, there are many stains on the internal organs of flies everywhere on the table and white wall, which is very ugly and unsanitary.

Last year, we joined the scientific and technological activity group, and the tutor organized us to carry out small invention activities, encouraging us to use our brains to find small invention topics and find ways to solve difficult problems in the topics. We will bring the above problems to the science and technology group for discussion. Under the guidance of the teacher, we will discuss the solution to this difficult problem in a word. We thought about several ways, and finally everyone agreed to add several rows of dots to the fly swatter, the height of which is slightly shorter than the size of the fly. In this way, the fly will be killed when it is hit, and there will be no annoying stains on the desktop and walls. The effect is very good, which is well received by teachers and parents.

The invention adds several rows of dots (all-purpose glue drops) on the common fly swatter, which solves the problem of stains left when the common fly swatter swats flies, and is a creative contribution of the invention. Because it won't leave a stain on flies, we named this invention "pollution-free fly swatter", and we suggest that the plastic factory produce this pollution-free fly swatter in the future.