Physics is a natural subject with a long history. With the development of science and technology and the progress of society, physics has penetrated into all fields of human life; Physics exists around physicists; Physics also exists around students; In learning, students should establish scientific consciousness, focus on the overall situation, start from small things, gradually master scientific learning methods and train scientific thinking methods through observation, thinking, practice and innovation, and soon you will have the mind of a scientist, laying a solid foundation for your amazing development and beautiful life in the future.

Science is everywhere in our lives: the squeak when we take off our sweaters in winter; Putting a coin on a cup full of water won't sink ... all this is waiting for us to discover and explore. We should learn to be "spies" in life and explore the mysteries.

Once, I helped my mother cook in the kitchen. I didn't expect to be very busy, but I also helped-mixing peppers with salt. Okay, it's over. The particles of salt and pepper are so small that I can't separate them in a short time. Now, I only have two ways. One is to patiently separate bit by bit; The second is to pour salt and pepper into a small box with holes to let the pepper leak out; The third is to separate them by scientific means.

I brought two dry plates. I put on disposable gloves and separated them bit by bit. But in less than two minutes, my hands and feet became numb. Look at the food, there is only a few salts. I suddenly lost confidence in this move like a deflated ball.

The first move is useless, so we have to take the second move.

We pour pepper and salt into the small box and shake it vigorously. We thought there was a hole in the box. Pepper was smaller than salt, and pepper leaked out of the hole, while salt was bigger than pepper and wouldn't fall off. But we are wrong, this method can't separate them well. Either the hole is too small, so that neither pepper nor salt leaks out, or the hole is too big, so that both pepper and salt leak out.

It still didn't work. What else can we do? At this time, Zhu Yilin said, "If only pepper were iron filings, we can separate them with magnets." "Yes, we can use suction. We have done scientific experiments on friction electrification. When we take off our sweater in winter, it will make a squeaking sound and stick dandruff and hair on the bed to the sweater. " Why don't we separate salt and pepper by triboelectrification?

I found a small plastic spoon and a small plate to use.

This time, I took a small plastic spoon and rubbed it on my clothes to make it generate static electricity, so as to achieve the effect of sucking pepper. After rubbing for a certain time, I put the spoon on the salt and pepper. As I expected, the pepper stuck to the bottom of the spoon like a demon, and finally I felt that the pepper was firmly adsorbed on the spoon.

This is really a miracle! I quickly put the pepper on a small plate prepared in advance and shouted, "I succeeded!" " I made it! "It turned out that the plastic spoon rubbed on the clothes and generated static electricity. Because pepper is lighter than salt, it sucks!

With the development of science and technology and the progress of society, physics has penetrated into all fields of human life.

For example:

1. The rearview mirror outside the driver's cab is convex.

By using the divergent function of convex mirror to light and the characteristics of upright, narrow and virtual image, the objects you see are small and the observation range is wider, thus ensuring driving safety.

2. The reflector of automobile headlights is a concave mirror.

It is made by using the property that concave mirror can reflect the light from the light source placed at its focus into parallel light.

Car headlights should always be equipped with glass lampshades with horizontal and vertical stripes.

Car headlights consists of a light bulb, a reflector and a front glass cover. According to the knowledge of lens and prism, car headlights glass cover is equivalent to the combination of lens and prism. When driving at night, drivers should not only see the road ahead, but also see the fixers, road signs, forks and so on. The lens and prism refract the light, so the lampshade diffuses the light to the required direction according to the actual needs, so that the light illuminates the road in front of the car and the roadside scenery evenly and softly. At the same time, this astigmatism lampshade can slightly refract some light to illuminate road signs and milestones, thus ensuring driving safety.

After the car is fitted with brown glass, it is difficult for pedestrians to see the faces of people in the car.

The tawny glass can reflect some light and absorb some light, so the light penetrating into the car is very weak. In order to see the passenger's face clearly, it is necessary to reflect enough light from the face and transmit it to the outside of the glass. Because the light inside the car is weak and there is not enough light to transmit, it is difficult to see the passenger's face clearly.

Except buses, the front windows of most cars are inclined.

When the front window glass of a car is tilted, the image of the passenger in the car reflected by the glass is in front of the country, and pedestrians on the road can't appear in the air above, so the image of the passenger in the car is separated from the pedestrians on the road, and the driver won't have an illusion. The front window of a bus is much higher than that of a car. Even the vertically installed front window looks the same height as the window, and pedestrians on the road cannot appear at this height, so drivers will not confuse the image of passengers outside the window with pedestrians on the road.

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 pork 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,

When the pot is filled with cold water, the water droplets attached to the outer surface of the pot bottom can only be dried 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. 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.

Spiced tea eggs are very popular with people, especially when it is hot. Careful people will find that when the eggs are just taken out of the boiling gravy, if they are eager to shell and eat them, it is inevitable to peel them off with the "meat". To solve this problem, there is a trick, that is, soak the eggs just out of the pot in cold water for a while, and then peel them, so that the eggshells can be peeled easily.

General substances (with a few exceptions) have the characteristics of thermal expansion and cold contraction. However, when different substances are heated or cooled, the speed and amplitude of expansion and contraction are different. Generally speaking, substances with low density are easier to expand and contract than substances with high density, and substances with fast heat transfer are easier to expand and contract than substances with slow heat transfer. An egg consists of a hard shell, a soft protein and a yolk, and their expansion and contraction are different. When the temperature changes slightly or slowly and evenly, nothing can be displayed; Once the temperature changes dramatically, the expansion and contraction speeds of eggshells and protein are inconsistent. When the boiled egg is immediately immersed in cold water, the temperature of the eggshell will decrease and shrink rapidly, while protein is still at its original temperature and does not shrink. At this time, a small part of protein will be squeezed into the short position of the egg by the eggshell. Then, due to the decrease of temperature, protein gradually contracted. By this time, the contraction of the eggshell was already very slow, and protein was separated from the eggshell. Therefore, when peeling, the shell and the "meat" will not come off together.

After that, let's talk about the formation of snow, fog, frost and steam.

The water in rivers, lakes and seas, after being irradiated by sunlight, constantly turns into steam and floats in the air. Air containing water vapor is heated and rises to a certain height. A cloud that condenses into suspended water droplets when it meets cold air is called a cloud. When the weather is cold, the water vapor near the ground can form a cloud of suspended water droplets. This is fog. So clouds and fog are essentially the same. Under the right conditions, the small water droplets in the cloud continue to merge into large water droplets until the rising airflow can't hold down, and then fall down to form rain. If it is winter, these water droplets will crystallize into snowflakes and fly all over the sky. However, the condensation of saturated water vapor in the air must have its condensation "core", that is, dust floating in the air, which is one of the necessary conditions to promote the formation of clouds, fog, rain and snow.

We all know the difference between raw eggs and cooked eggs, but do you know the secret?

Put the egg on the table and twist it quickly by hand. Observe its rotation after leaving the hand: if the egg rotates smoothly, it is a cooked egg; Conversely, if the rotation is not smooth, it is a raw egg.

Because the yolk of the boiled egg is twisted together when it is twisted, it turns smoothly. On the contrary, when a raw egg is twisted, only the shell is stressed, while protein and yolk are hardly stressed. According to Newton's first law, protein and yolk are almost motionless because of inertia. As a result, the rotation of the eggshell was slowed down by protein.