Collection of scientific knowledge in everyday life

Sound is one of main ways a person receives information, and sound conveys to us not only linguistic information. Below are some applications and principles of sound in other aspects.

1. Discuss and analyze familiar visitors

Phenomena: when person you live with is talking outside, we can tell who is talking by their voice.

Principle: The pitch and volume of voices of different people may be same, but timbre will never be same, because timbres of sounds from different sounding bodies are usually different. Because we are very familiar with them, we can determine timbre by distinguishing timbre. We can tell who is talking.

2 listening lengths

Phenomena: when pouring water into a thermos, you can tell if water is full by sound.

Principle: Different lengths of air columns have different sound frequencies when they vibrate and sound. The longer air column, lower tone; The higher tone, especially when water has just been filled, tone will rise sharply. By listening to pitch of sound, we can tell that water is full.

3 Select elements

Phenomena: When we go to store to buy bowls and china, we tap china with our hands or other objects, and we can judge good ringing of china by sound.

Principle: The timbre of cracked bowls and basins is much worse than that of ordinary porcelain. Bad bowls and basins can be distinguished by their timbre. Of course, method of distinguishing tone and observing form is also used, but mainly differs in timbre.

4 Measuring Distance

Phenomena: If there is a building or a high mountain ahead, yell at a high mountain, measure time from sound to moment sound is heard with a clock, and use speed of sound to measure physical distance. between us and a high mountain or a tall building.

Principle: An echo is generated when sound hits an obstacle during transmission and is reflected back.

5 See a doctor

Phenomena 1: Stethoscope

Principle: The sounds made by some organs in human body, such as heart, lungs, trachea, stomach, etc., when diseases occur, sounds made by organs according to certain characteristics, and doctor can hear it through a stethoscope, and diagnose diseases accordingly.

Phenomena 2: Principle of B-ultrasound

Principle: Sound above 20,000 Hz is called ultrasound. The frequency and intensity of wave are determined, and an image is formed on TV screen, which provides an important basis for judging disease. That B-ultrasound uses echo principle.

6 Healing (energy transfer)

Phenomena: extracorporeal lithotripsy

Principle. Stones are found in some organs of human body such as kidneys and gallbladder. Extracorporeal lithotripter uses ultrasonic waves,which penetrate human body and cause quartz watch to vibrate violently, destroying it. It basically uses property that sound waves can transfer energy.

7 Providing information (disaster monitoring)

Phenomena: Information about earthquakes and typhoons can be obtained by monitoring infrasonic waves.

Principle: Infrasound is sound below 20 Hz that humans cannot hear. Some natural disasters, such as earthquakes, volcanic eruptions, typhoons, etc., are accompanied by generation of infrasonic waves, infrasonic waves are very little inhibited during propagation, so they can propagate over long distances, and information about some natural disasters can be obtained by monitoring transmitted infrasonic waves .

Analysis: If front wheels touch ground first, motorcycle will continue to coast forward and motorcycle will rotate clockwise with front wheels as pivot point, resulting in a rollover accident; if rear wheels touch ground first, it will have effect of turning motorcycle clockwise with rear wheel as turning point, so that front wheel will also land quickly, thus avoiding rollover accidents.

2. How to distinguish raw eggs from boiled eggs using simple physical methods

Analysis: After placing two eggs on a relatively smooth table, turn eggs at same time with about same force. The first stop is raw egg and last is boiled egg. The difference between raw and boiled eggs is that contents of egg are liquid and solid. When eggshell becomes hard, eggshell starts to rotate under force, and liquid content remains stationary due to inertia There is a certain frictional resistance between them, and also frictional resistance between eggshell and table, so it will stop rotating soon. Boiled egg content is solid , and eggshell is self-sufficient. When eggshell becomes hard, eggshell and contents rotate together and there is no relative motion between them. You just need to overcome a little friction on table. so that it can rotate for a long time.

3. The lifting machine can separate grains, chaff and small stones

Principle 1: Although grains and small stones of same size are thrown out at same speed, their inertia is different due to their different masses. Overcome air resistance and fly further.

Principle 2: grains and small stones of same size fly out at same speed, but because of their different masses, their kinetic energy is different. The resistance flies to a more distant place.

4. The kitchen sink sewer pipe is clogged and people often use "suction" to deal with it. This instrument consists of a wooden handle and a hemispherical rubber bowl. Cover rubber bowl with mouth of drain pipe, press wooden handle to smooth leather bowl, open faucet to fill pool with water, quickly pull rubber bowl up, blockage will loosen and drain

Analysis: When pressing wooden handle to flatten cup, some of air from cup can be squeezed out, and space between blockage and cup is relatively small. After pool is filled with water, when bowl rises quickly, space between blockage and bowl suddenly becomes larger, so that gas pressure between them becomes smaller, which is less than atmospheric pressure under blockage, and atmospheric pressure lift blockage to loosen it, and at that moment a large amount of water will rush down, washing away blockage, so that pipeline can be opened.

Physical knowledge is closely related to our life. It is very important to observe physical phenomena occurring at any moment of everyday life, analyze and investigate reasons for their formation, and find out patterns. Let's talk about some of physics related to water pipes.

1. Why does water come out when you turn on faucet?

It turns out that most of water from water pipes in home comes from water tower, and water in water tower is pushed out by a high pressure pump. Therefore, surface of water in water tower must be much higher than surface of water in faucet. The faucet and water tower form a connector. According to connection principle, liquid level must be even, so when faucet is turned on, water will flow out.

Second, when I press a water pipe, why do I sometimes hear 2 sounds and sometimes 3?

As we all know, sound travels at different speeds in different environments. In general, fastest propagation is in a solid, for example, 5200 meters per second in steel; secondly, in a liquid, for example, in water 1500 meters per second; slowest propagation in air, only 340 meters per second. It can be seen that if there is no water in water pipe and knock on other end of water pipe, then sound transmission medium is air and a water pipe, and we can hear two sounds. If there is water in plumbing, and sound transmission medium is air, water, and plumbing, we can hear sound three times. We can also use this method to determine if there is water in a water pipe.

3. In cold winters, sometimes when you turn on a faucet, you will find that not a drop of water will come out, and sometimes plumbing will "freeze and crack." Why?

It turned out that water in plumbing was frozen and frozen in form of ice, so not a single drop could leak out. As quality of frozen water remains same, density becomes less and volume increases, which is why water pipes sometimes "freeze and crack". We can wrap a layer of anti-freeze plastic paper on outside of water pipe, but safest way is to open faucet a little and let water drip slowly so it doesn't freeze.

4. In cold weather, when touching a metal pipe of tap water, it seems that hand seems to be "sticky". What is reason?

It turns out that metal pipe of tap water is a good conductor of heat. When you touch it with your hand, heat on your hand is quickly absorbed by metal and removed to side. The tubes are "glued" together.

5. How to identify pipes of cold and hot water in bathroom?

It's cold, when we go to bathroom to take a shower, we will find two pipes for water supply, one cold and one hot. We really want to know which pipecold water, and what with hot, what should we do if we touch them directly and are afraid of getting burned? In fact, attentive people will find that surfaces of two water pipes are different. One of them has a layer of water droplets on surface, and other does not. What is reason for this? It turns out that bathroom is filled with a large amount of high-temperature water vapor, which liquefies into a layer of fine water droplets and sticks to surface of the plumbing when it encounters a pipe with cold water. "sweating" water pipe is a cold water pipe.