Physics knowledge in life

In the long study career, everyone has memorized a lot of knowledge points, and they must be very familiar with them! Knowledge points can also be understood in a popular way as important content. Want a compiled knowledge point? The following is the physics knowledge in life that I have compiled. It is for reference only. I hope it can help everyone. Physics knowledge in life 1

1. Phenomena related to mechanics knowledge

1. The spout and belly of the electric kettle form a connector, and the water surface is always level.

2. The thin blade of the kitchen knife is to reduce the force-bearing area and increase the pressure.

3. The blade of the kitchen knife is oiled to smooth the contact surface and reduce friction when cutting vegetables.

4. Kitchen knife handles, spatula handles, and electric kettle handles have convex and concave patterns, which make the contact surface rough and increase friction.

5. When the fire shovel delivers coal, the inertia of the coal is used to deliver the coal into the furnace.

6. Pour boiling water into the thermos bottle and know the amount of water based on the sound. As the amount of water increases, the length of the air column decreases, the vibration frequency increases, and the pitch rises.

7. When sharpening a kitchen knife, you need to keep watering it. This is because the friction between the kitchen knife and the stone produces heat, which increases the internal energy of the knife. As the temperature rises, the hardness of the knife edge becomes smaller and the knife edge becomes unfavorable. Watering uses heat. The transfer reduces the internal energy of the kitchen knife and lowers the temperature without rising too high.

2. Phenomena related to electrical knowledge

1. Electric rice cooker cooking, electric wok cooking, and electric kettle boiling water use electric energy to convert into internal energy. They are all Use heat transfer to cook rice, vegetables, and boil water.

2. The exhaust fan (range hood) uses electrical energy to convert into mechanical energy, and uses air convection to transform the air.

3. Insert the three-pin plugs of rice cookers, electric woks, and electric kettles into three-hole sockets to prevent electrical leakage and electric shock accidents.

4. The microwave oven heats evenly, has high thermal efficiency, and is hygienic and pollution-free. The heating principle is to convert electrical energy into electromagnetic energy, and then convert electromagnetic energy into internal energy.

5. The electric lights in the kitchen work by utilizing the thermal effect of current to convert electrical energy into internal energy and light energy.

6. Kitchen stoves (briquette stoves, liquefied gas stoves, coal stoves, wood stoves) convert chemical energy into internal energy, that is, the fuel burns to release heat. Physics knowledge in life 2

As long as we carefully observe the physical phenomena around us in daily life and production, connect it with the physical knowledge we have learned, and analyze and explain these phenomena, we can improve our observation and analysis skills. and problem-solving skills. Truly let "physics move to life, and life move to society"!

1. Application of mechanical knowledge in life

When the wind blows, in order to prevent the clothes drying on the wire from stacking or falling off, you can first tie a loop with a plastic rope. Then put this rope loop on the wire, and hang the clothes hanger on the loop so that the clothes hanger will not slide easily. The purpose is to increase the force-bearing area between the rope loop sleeve and the iron wire to increase resistance.

When sharpening a kitchen knife, you need to keep watering it, because the friction between the kitchen knife and the stone generates heat, which increases the internal energy of the knife, increases the temperature, and reduces the hardness of the knife edge, which is detrimental to the knife edge. Watering uses heat transfer to reduce the internal energy of the kitchen knife and lower the temperature without rising too high.

2. Application of thermal knowledge in life

When boiling water, in order to save time and electricity consumption, you can add a little hot water first. The purpose of this is to speed up the movement of molecules and accelerate their diffusion.

When frying lean meat slices, if the meat slices are directly placed into a hot oil pan for frying, the water contained in the lean meat fiber will evaporate rapidly, causing the meat slices to become dry and hard. In order to stir-fry the meat slices deliciously, chefs often mix the meat slices with an appropriate amount of starch in advance. After the meat slices are placed in the hot oil pan, the water in the starch paste attached to the outside of the meat slices evaporates, while the water in the meat slices is difficult to evaporate. , still maintaining the tenderness of the meat.

3. Application of acoustic knowledge in daily life

Nowadays, residential buildings are generally equipped with anti-theft nets, and above the nets there is a rain shield made of a large thin iron sheet. board, so that the things inside the anti-theft net will not get wet. However, whenever it rains, the raindrops hit the rain shield and make a loud clicking sound. At night, this noise affects people's sleep. If you put a sponge on the iron sheet, then the noise can be eliminated. decreased.

When we go to the store to buy bowls and porcelain, we tap the porcelain with our hands or other objects, and we can judge the quality of the porcelain by the sound.

4. Application of optical knowledge in life

When washing a car under the scorching sun, the convex lens effect formed by water droplets will cause local high temperature in the top layer of the car paint. Car paint will lose its luster over time. If waxing is done at this time, it will easily cause uneven color of the car body. Car washes are generally done in the evening or in a cool place.

When taking pictures facing the TV screen, you should turn off the camera flash and indoor lighting, so that the picture will be clearer. Because the reflected light from the flash and lighting on the TV screen will interfere with the transmitted light of the TV picture.

5. Utilization of electrical knowledge in life

Make full use of the waste heat of the rice cooker. When cooking rice, when the pot boils, lift the button to cut off the power, use the residual heat from the electric hot plate, wait a few minutes and then press the button again. The rice cooker will automatically cut off the power after the rice is cooked.

Do not leave household appliances in standby mode. If household appliances are in standby mode, it will consume power and damage the machine. When watching TV, turn down the volume and brightness as much as possible to save power and make your eyes less likely to tire. After shutting down, because the remote control receiving part is still charged and the indicator light is on, some power will be consumed, so the power plug should be unplugged after shutting down.

In short, as long as we carefully observe the physical phenomena around us and use our brains in life, physical knowledge will fully serve us. Physics knowledge in life 3

The phenomenon of a charged object losing its charge is called discharge. Common discharge phenomena include the following:

1. Ground discharge

The earth is a good conductor. Because it is extremely large, it can accept a large amount of charge without significantly changing the earth's potential. , just like pumping water from the ocean or releasing water into the ocean, it cannot significantly change the height of the sea level. If a charged conductor is connected to the earth with a wire, charge will flow from the charged body to the earth until the conductor is so charged that it can be considered to be no longer charged. (If the conductor is positively charged, free electrons actually flow from the earth to the conductor. This is equivalent to the positive charge flowing from the conductor to the earth.)

In production and in real life, it is often necessary to avoid the accumulation of charges. This Grounding is an effective measure.

2 Tip Discharge

Normally, air is non-conductive, but if the electric field is particularly strong, the positive and negative charges in the air molecules are subject to strong electric field forces in opposite directions and may be Tear apart, this phenomenon is called ionization of air. Because the ionized air has charges that can move freely, the air can conduct electricity. The negative charges generated after ionization of air are electrons, and the atoms that have lost electrons are positively charged and are called positive ions.

Since the same kind of charges repel each other, the static charges on the conductor are always distributed on the surface, and generally speaking, the distribution is uneven (Figure 2). The charge at the tip of the conductor is particularly dense, so near the tip The electric field in the air is particularly strong, causing the small number of ions remaining in the air to accelerate. These high-speed ions hit air molecules, ionizing more molecules. At this time, the air becomes a conductor, resulting in tip discharge.

Tip discharge is of great significance in technology. The surfaces of high-voltage transmission conductors and metal components of high-voltage equipment must be smooth to avoid loss of electrical energy or accidents due to tip discharge.

3. Spark discharge

When a high-voltage charged object and a conductor are very close to each other, the strong electric field will instantly ionize the air between them, and the charge will form an electric current through the ionized air. Because the current is particularly large, a large amount of heat is generated, causing the air to sound and glow, producing electric sparks. This discharge phenomenon is called spark discharge.

Spark discharge is often encountered in life. In dry winter, when you wear sweaters and chemical fiber clothes and walk for a long time, static charges will accumulate on your body due to friction. At this time, if your fingers are close to metal objects, you will feel a pinprick-like pain in your hands. This is caused by spark discharge. If you take a key beforehand and keep the tip of the key close to other metal objects, you will avoid pain. Try it in a dark place. When the tip of the key is close to the metal body, you will not only hear a sound, but also see sparks.

In some factories or laboratories, where there is a large amount of flammable gas, workers have to wear special shoes. These shoes have very good electrical conductivity and can lead charges into the earth to prevent charges from being transferred to the human body. accumulation to avoid spark discharge and fire. Physics knowledge in life 4

1. Why is the sky red in the morning and evening?

In the morning and evening, colorful clouds often appear on the horizon around sunrise and sunset. The formation of morning glow and sunset glow is due to the scattering of light by air. When sunlight enters the atmosphere, it is scattered when it encounters atmospheric molecules and particles suspended in the atmosphere. These atmospheric molecules and particles themselves do not emit light, but because they scatter sunlight, each atmospheric molecule forms a scattered light source. Light in the solar spectrum with shorter wavelengths such as purple, blue, and cyan is the easiest to scatter, while light with longer wavelengths such as red, orange, and yellow has strong transmittance. After these rays are scattered by impurities such as air molecules and water vapor, the sky there takes on brilliant colors.

2. What causes the rainbow to form? Why is the rainbow arched?

(1) Rainbows are caused by the emission and refraction of sunlight hitting water droplets in the air.

(2) When the atmospheric conditions reach the point where a rainbow is formed, the rainbow is actually ring-shaped. But due to the obstruction of the horizon, we can only see half of the ring at most. At the same time, because the conditions in the atmosphere are different everywhere, in most cases we can only see a small arc. There are few obstructions at sea and the atmospheric conditions are relatively consistent over a large area, so you can often see a complete semicircle of a rainbow.

3. What is the reason why snow does not turn cold when it snows?

Snowing and melting snow are a process of solidification and melting; solidification is an exothermic process, so it will naturally not be cold, while melting is an endothermic process; so snow does not cool and melts. cold.

4. Real gold is not afraid of fire

Judging from the melting point of gold, although it is not the highest, it is still 1068°C, while the temperature of a general flame is about 800°C. The temperature of the flame is less than the melting point of gold, so gold cannot melt.

5. The boiling water does not make a sound, the sounding water does not boil

Before the water boils, due to convection, the bubbles in the water rise while vibrating up and down, and most of the bubbles burst under the pressure in the water. , the cracking sound and vibration sound resonate with the container, so the sound is very loud. After the water boils, the upper and lower parts are isothermal, and the bubble volume increases. Under the action of buoyancy, it rises to the water surface before bursting, so the sound is relatively small.

6. Water and fire are incompatible

For substances to burn, they must reach the ignition point. Due to the large specific heat of water, contact between water and fire can absorb a large amount of heat, so that the temperature of the ignited object decreases; At the same time, the vaporized water vapor surrounds the burning object, making it impossible for the object to come into contact with air. Without air, combustion cannot proceed.

7. Travel 80,000 miles a day while sitting on the ground

Since the radius of the earth is 6370 kilometers, every time the earth rotates once, the distance "traveled" by objects on its surface is about 40003.6 Kilometers, about 80,000 miles.

8. Auspicious snow brings good harvest

The snow that falls on the ground has many loose gaps, which are filled with stagnant air and are poor conductors of heat. When it covers crops, When used, it can well prevent heat conduction and air convection, so it can play a thermal insulation role.

9. The sun can be seen with a drop of water

A drop of water is equivalent to a convex lens. According to the imaging rules of convex lenses, through a drop of water, the image of the sun can be seen, and the image of the sun can be seen from the small.

10. There must be wind next to the fire

The air near the fire expands and rises when heated, and the cold air in the distance will fill in. The flow of hot and cold air forms wind.

11. Mercury falls to the ground and penetrates everywhere.

The density of mercury is greater than the density of the materials that make up the ground. Mercury is fluid, so it always sinks under other materials.

Physics knowledge in life 5

Sometimes we are surprised that many things should develop in the usual direction, but this is not the case. A lot of common sense is actually some physical phenomena. Sometimes conditions do not allow or When conditions change, things will not change according to common sense. Let’s share some interesting physics knowledge.

1. When heating cold porridge or cold rice, the pot makes a "plop, plop" sound and bubbles keep coming out. However, when you taste it, the porridge or rice is not hot. This is why. ?

Heating cold porridge or rice is different from boiling water. Although water is a bad body for heat and conducts heat very slowly, water has very good fluidity. When the water at the bottom of the pot is heated, it expands, floats when its density decreases, and the surrounding cold water flows to fill it. Through this convection, the heat at the bottom of the pot is continuously transferred to all parts of the water, causing the water to change. hot. However, cold porridge or rice has poor fluidity and is not easy to conduct heat. Therefore, when the porridge or rice at the bottom of the pot absorbs heat, the temperature rises quickly, but it cannot flow upward or around quickly. A large amount of heat is concentrated at the bottom of the pot and burns the porridge at the bottom of the pot. Because heat is difficult to transfer to the top of the porridge, the porridge on top is still cold. When heating cold porridge or rice, add more water to the pot to thin the porridge and enhance its fluidity. In addition, stir frequently to force convection so that the porridge can be heated evenly.

2. When cooking meat or making soup in a casserole, when the soup is taken off the stove after boiling, the soup will continue to boil for a while, but this phenomenon does not occur in iron and aluminum pots. This is Why?

Because the casserole is made of clay, the specific heat of non-metal is much greater than that of metal, and the heat transfer capacity is much worse than that of metal. When the casserole is heated on the stove, the temperature of the outer layer of the pot greatly exceeds 100°C, and the temperature of the inner layer is slightly higher than 100°C. At this time, the pot absorbs a lot of heat and stores a lot of thermal energy. After taking the casserole off the stove, the outer layer of the pot, which is well above 100°C, continues to transfer heat to the inner layer, so that the soup in the pot still reaches 100°C and can continue to boil for a period of time. Iron and aluminum pots will not This phenomenon occurs (students are asked to analyze the reasons themselves).

3. "Familiar with each other" in stir-fried meat. During festivals, people always stir-fry some meat and vegetables, so how to stir-fry meat slices?

If you put the meat slices directly into a hot oil pan for stir-frying, the water contained in the lean meat fiber will evaporate rapidly, causing the meat slices to become dry and hard, and even the meat will be charred and fried. Paste, the flavor is greatly lost. In order to stir-fry the meat slices deliciously, chefs often mix the meat slices with an appropriate amount of starch in advance. After the meat slices are placed in the hot oil pan, the water in the starch paste attached to the outside of the meat slices evaporates, but the water in the meat slices is difficult to evaporate. , the original tenderness of the meat is still maintained, and the loss of nutrients is reduced. The meat is cooked quickly and is "cooked upon meeting the eyes". The meat slices fried in this way are both tender, delicious and nutritious.

4. What is the best way to thaw frozen meat? How to defrost frozen meat and chicken when you take them out of the refrigerator?

It is best to use cold water close to 0℃. Because the temperature of frozen meat is below 0℃, if it is thawed in hot water, the frozen meat will absorb heat from the hot water, and its outer layer will thaw quickly and the temperature will quickly rise above 0℃. With gaps, the ability to transfer heat is reduced, making it difficult for the frozen meat inside to absorb heat and thaw to form a hard core. If frozen meat is placed in cold water, the temperature of the cold water will quickly drop to 0°C due to the heat absorbed by the frozen meat and frozen chicken, and some of the water will freeze. Because 1 gram of water can release 80 calories when it freezes (and 1 gram of water only releases 1 calorie when it is lowered by 1°C). After so much heat released is absorbed by the frozen meat, the temperature of the outer layer of the meat rises quickly. , and the inner layer easily absorbs heat, so the temperature of the whole piece of meat rises to 0°C relatively quickly. Repeat this several times until the frozen meat is defrosted. From a nutritional perspective, this method of uniform and slow heating is also scientific. Physics knowledge in life 6

Pressure

(1) Human teeth use the knowledge of pressure. Human incisors and canines are relatively pointed, and the crowns of bicuspids and molars have pointed protrusions. These are ways to reduce the stress-bearing area and increase pressure, making it easier for people to bite off or chew food.

(2) Human feet have different sizes. The general rule is that taller people have larger feet. This ensures that people with different weights have basically the same pressure on the ground when they walk.

(3) When a person inhales, the chest muscles increase the volume of the chest cavity, the volume of a certain mass of gas in the lungs increases, and the pressure decreases, which is less than the external atmospheric pressure. The atmospheric pressure presses the air into the respiratory tract and enters the human body. In the alveoli of the lungs; when a person exhales, the chest muscles contract the chest cavity and compress the lungs to reduce their volume. The volume of gas in the lungs decreases and the pressure increases, which is greater than the atmospheric pressure, thereby exhaling carbon dioxide.

(4) The flow of human blood depends on the pressure generated by the contraction of the heart.

Friction

(1) In the human mouth, the surface of the tongue is rough, and there are also lines on the palate. These structures increase the friction with food and facilitate stirring of food. Or put food into the esophagus.

(2) People have special palm prints on their palms and soles. When the grip strength is constant, the fingerprints and palmprints on the palm can increase the friction with the contact object, making it easier for the person to grasp the object. Patterns on the soles of the feet can increase friction, making it easier for people to walk without their feet slipping against socks and shoes.

(3) When a person walks, friction occurs between the foot and the ground. When the foot pushes back hard, it tends to move backward relative to the ground. When the ground faces the sole of the shoe, it hinders the movement of the foot relative to the ground. The frictional resistance of the ground moving backward, this force moves forward, and it is this force that makes people move forward.

Simple Machine

The human forearm is a laborious lever. The elbow joint is its fulcrum. When lifting something, the gravity of the object is the resistance acting on it, and the force exerted by the biceps is its driving force.

Energy

(1) When people eat food, after digestion, large molecules that cannot be directly absorbed by people are converted into small molecules that can be absorbed and utilized by people and enter through the digestive tract. Cells, chemical changes occur in cells, converting biomass energy into chemical energy for human use.

(2) Human physiological curvature (neck curvature, chest curvature, lumbar curvature and sacral curvature), as well as the curvature of human foot arches, femurs and tibias, just like the springs under a bicycle seat, It can convert the kinetic energy of people's up and down movement during walking or jumping into elastic potential energy, which can effectively reduce the impact of vibration on the brain during walking.

Thermal Science

(1) When people engage in intense activities for a long time, the human body will generate a lot of heat. If this heat is not dissipated in time, it will cause the normal physiological activities of the person to be destroyed. The sweat glands of the human body will secrete sweat in time. The evaporation of sweat absorbs a large amount of heat from the human body, keeping the human body temperature at a constant temperature of 37°C. When the weather temperature is high and it is difficult for the human body to dissipate heat, the human body will also dissipate heat by sweating a lot.

(2) Hair not only makes you more beautiful, but also regulates body temperature and protects the brain. In winter, the cold wind constricts blood vessels, and hair can keep the head a certain amount of heat; in summer, when the sun is scorching, hair can block the damage to the scalp caused by direct sunlight. At the same time, blood vessels expand, and hair can help dissipate heat. Therefore, hair has the dual function of retaining heat and dissipating heat.

Optics

(1) The human eye is the most sensitive “camera”. The pupil of the eye is like the aperture of a camera, its size will change with different intensity of light; the lens is like a convex lens, and its focal length can be changed; the retina is like a "film". For normal eyes, when a person looks at distant objects, the curvature of the lens decreases and the focal length becomes larger; when a person looks at a nearby object, the curvature of the lens becomes larger and the focal length becomes smaller, so that the image can always be clearly formed on the retina. superior.

(2) The human body has a constant temperature and emits infrared rays of a certain wavelength. However, when there is inflammation somewhere in the human body and the temperature increases locally, the intensity of the emitted infrared rays will change. Therefore, medically, infrared photos can be taken to aid diagnosis.

(3) Human eyes determine the specific location of objects based on the straight-line propagation of light. When a person looks at an object with one eye, not only is he unable to see clearly with both eyes, but when looking against the light, he cannot determine the distance of the object from the person, and therefore cannot determine the exact location of the object; when looking with two eyes together , look against the light, and the position where the light crosses is the position of the object.

Electricity

The human body has bioelectric currents. Using medical equipment to detect human bioelectric currents can help you understand whether human tissues are working normally. For example: medical electrocardiogram and electroencephalogram are made based on this phenomenon.

The lie detector also makes judgments based on changes in the human body's current. When a person is lying, the human body's bioelectric current will undergo abnormal changes. Based on the bioelectric current, it can be judged whether the person being tested is lying.

Acoustics

(1) Human vocal cords vibrate and produce sounds, enabling language communication between people. Different people have different vocal cords, which produce different timbres when they speak. We can identify who is speaking based on the timbre.

(2) The human ear is a hearing organ, and sound is transmitted to the human ear through the vibration of the air. The vibrating air causes the eardrum to vibrate, and the eardrum transmits the vibration to the ossicles and the auditory nerve to the brain, forming hearing.

(3) The transmission of sound requires a medium. Human bones can transmit sound. If you have conductive deafness alone, you can use bone conduction to hear the sound.

(4) People’s binaural effect helps people judge the location of sound sources. The distance from the sound source to the two ears is generally different, and the characteristics such as the time and intensity of the sound reaching the two ears are also different. Based on these differences, people can judge the location of the sound source. Physics knowledge in life 7

1. Why do bicycle tires have uneven patterns?

The amount of friction is related to two factors: the amount of pressure and the roughness of the contact surface. degree. The greater the pressure, the greater the friction; the rougher the contact surface, the greater the friction. Bicycle tires have uneven patterns, which increase friction by increasing the roughness between the bicycle and the ground. Its purpose is to prevent the bicycle from slipping.

2. Why should we wear sunscreen?

Utilize the principles of physics and rely on the reflection effect of physical sunscreen agents (common ones include titanium dioxide and zinc oxide) to block ultraviolet rays and achieve the purpose of sun protection. Simply put, it uses reflective particles to form a protective wall on the surface of the skin, so that the skin no longer absorbs ultraviolet rays.

3. Why should the window glass on the front of the car be tilted?

From Analyzing from an optical perspective: the windshield is transparent, but it is not absolutely reflection-free. Passengers sitting behind the driver will be imaged in front of the driver due to reflection. The car is relatively short, and the passengers sitting inside are reflected in the front through the windshield. If the windshield is vertical, the image will be about the same height as the pedestrians in front of the car, which will interfere with the driver's visual judgment. When the windshield is tilted, the image formed will be above the front of the car, which will not affect visual judgment and ensure driving safety.

4. Why do incandescent lamps need to be pear-shaped?

The filament of the light bulb is made of tungsten metal. The filament generates heat, with temperatures reaching over 2500°C. Metal tungsten sublimates at high temperatures, and part of the metal tungsten particles escape from the surface of the filament and settle on the inner wall of the bulb. Over time, the bulb will darken, reducing brightness and affecting lighting. According to the characteristics of gas convection moving downward and upward, a small amount of inert gas is filled in the bulb and the bulb is made into a pear shape. In this way, when the inert gas in the bulb convects, most of the black particles evaporated from the metal tungsten are rolled upward by the gas and deposited on the neck of the bulb, which can reduce the impact on the surrounding and bottom of the bulb, so that the brightness of the bulb is not affected.

5. Why do you need to turn off the lights in the car when driving at night?

This mainly depends on the brightness of the external environment. Whether you turn on the lights inside during the day has no impact on driving. But it doesn't work at night, because for glass, when one side is dark and the other is bright, a mirror will be formed on the bright side. Therefore, when driving at night and turning on the lights inside, the outside of the car is dark, and the glass becomes a mirror. You cannot see clearly outside the car, and what you see is the image inside the car, which is not conducive to driving. So turn off the lights inside the car so that the driver can see the road conditions outside the car clearly.