Physics questions on acoustic phenomena in the second year of junior high school, and physics questi

Yes, when your velocity is equal to the speed of sound, that is, you are moving forward at the same time with the same sound wave band, which means that the sound waves that your ears receive are all the same, but because the sound waves disappear along the way, the sound you hear will become smaller and smaller until you can't hear it, and the intensity and frequency of the sound determine how long you hear it. If you are moving faster than the speed of sound, i.e. you are chasing the sound wave that has been emitted, you will hear a replay (i.e. reverse), and there may be a sound wave band that has died out by the time you catch it, so you will hear choppy sounds.

Yes, the speed of sound is 340m s in the air, you leave a conference that is playing at the speed of sound, and the sound wave leaves the assembly at the same speed as you, so the sound wave you hear is the sound wave you heard when you just left, but the sound wave will become smaller during the propagation process, so the sound wave will decrease as the time you leave increases, so you will not hear the sound after a while.

Looks like I'm misremembering .........Courierking should be correct Courierking is talking about the Doppler effect Since C University has answered the correct answer, but people who have not learned about the Doppler effect should not understand it, I will talk about it on the basis of C University

Sound waves can't be seen, so I'll make an analogy with water waves. The water waves spread round and round, everyone knows this. But if you look at just one point, you will see that the point is moving up and down.

The same is true for sound waves, which transmit sound by causing the next molecules to vibrate through molecules. When we move at the same speed as the speed of sound, analogous to water waves, our speed of movement and the speed of propagation of water waves are the same, we will only see a relatively stationary circle, this circle will not move up and down, that is, the water molecules are relatively stationary with us, and the vibrational frequency is zero.

Speaking of echo waves, in that wave, the air molecules that are driven are relatively stationary with us, so the sound frequency is zero, and we can't hear the sound

The score must be given a big C

Absolutely! The speed of a person is the same as the speed of a sound, let's say you hear it now"Pyridox"This sound, when you leave, is the same as the speed of the sound, and after 1 second, people from 340 meters (assuming in a temperature of 15 degrees) can hear it"Pyridox"This tone.

And if your speed is the same as the speed of the sound, then in 1 second you will be 340 meters away, and you will still hear this sound. And so on ...

If it's too fast, you might not hear it. But if it is a physics question in the second year of junior high school, the answer will not be so biased.

Kindness. I'm a sophomore in junior high school. I've finished the content of the previous volume. It's simple.

I think so. Because we have learned about motion in physics in the second year of junior high school, if we use it here, our speed is 340 s, and the speed of sound is also 340m s.

Sound travels through vibrations, and our ears also feel sound through vibrations.

The phenomenon of "high and low sound" (I suddenly forgot what it was called): the car drove past us at a constant speed, honking its horn as we drove along, and we noticed that the car was louder when it was driving towards us, and lower when it was far away from us;

Although the speed of sound is the same, the difference between the relative velocity of us and the object we are pronouncing causes us to perceive the sound it produces differently, and there is a rule: the frequency is high when approaching, the frequency is low when moving away from the speed of sound, and when moving away from the speed of sound, the frequency is as low as 0.

Our ears can't perceive sounds below 20 Hz, and sounds with a frequency of 0 are not actually sounds because they stop vibrating.

Look, can we hear this voice?

I don't think I can hear anything.

Although the speed of sound is 340 m s, the sound is produced by vibration, and the reason why the human ear can hear sound is that the eardrum feels the vibration of the air and produces the sound, which --- hearing. And when a person is moving at a speed equal to the speed of sound, the vibrations generated by the sound source should be stationary relative to the person's eardrum, so no sound can be heard.

I'm taking the test, this kind of question is too stupid, it's not good to pull a 1st or 2nd grade, too, you leave at the speed of sound, you may hear some words, but there will definitely be some because you are fast and can't hear it. The person who asked the question is not skilled, I don't know if you can understand it. Remember, the question is only with a junior high school student with better grades.

This phenomenon occurs because sound travels more slowly in the air than light travels through the air.

The conditions are not sufficient, only speed, there is no distance and time, so the formula of v=s t is not valid, that is, there is a problem with this question, my talent is limited, please invite another master.

Air, resonance, vibration, hold, sound is generated by vibration, ultrasonic flaw detection (ultrasound), image.

amplitude, gained energy,

1 Air, Vibration 2 Vibration Press and hold The object needs to vibrate 3 Ultrasonic flaw detection 4 Image Amplitude Timbre.

1。Air, vibration.

2。Vibrate, press the drum surface, vibration stops, stops occurs.

3。Do ultrasound.

4。Amplitude, frequency, obtained.

5。Vibration.

1.Air, vibration.

2.Vibration Hold down the drum face The sound is produced by the vibration of an object.

3.Ultrasonic welder.

4.The image amplitude obtained.

5.Timbre.

When a student was picking watermelons, he flicked them with his fingers a few times, and the sound was crisp and dull, and he judged the raw and ripe watermelons based on this. He applied his knowledge of physics (different timbres) to study the frequency relationship between the pitch of sound and the vibration of the emitter using a tuning fork and an oscilloscope. In this experiment, he conducted two experiments, the first time striking a tuning fork with a frequency of 512 Hz, and the second time striking a tuning fork with a frequency of 256 Hz with the same force, and the result was that the first sound was heard to be higher pitch.

The conclusion from this is that the faster the emitter vibrates, the higher the frequency, and the higher the pitch (optionally "high" or "low").

A student uses an oscilloscope, a hacksaw blade, and a vice to study the loudness of sound. As shown in the picture on the left below, he clamped the lower end of the hacksaw blade to the vice, and the upper end was pulled by hand to make the hacksaw blade vibrate and make a sound. In the experiment, he carried out two experiments, the first saw blade made a sound sound, the second saw blade made a light sound, and he observed that the amplitude of the waveform displayed on the oscilloscope is shown in the following figures (a) and (b) on the right, respectively, then he came to the experimental conclusion:

The greater the amplitude, the louder the sound, look.

Experiment Answers:

1.Tone. 2.Frequency high.

1。Assuming that the car is far from the high mountain x in front when the echo is heard, then x+(x+10*4m)=4*340m, and x=660m.

2。The velocity of the bullet when it leaves the muzzle is vm per second, then 340m (340m s) 340m v=

It is derived that v=680m s

I'm absolutely right, give it points.

For example, the speed of sound is the standard 340m s

It is known that v1=10m s v sound=340m s t=4s, find s s1 s2 s3 s4

Solution s=vsound*t=340m*4s=1360ms1=v1*t=10m*4s=40m

s2=s+s1=1360m+40m=1400ms3=1400m/2=700m

s4=700m-40m=660m

The second question is that the speed of sound is 340m s

It is known that s=340m vsound=340ms s=t=find t1 v

Solution: t sound = s v sound = 340m 340m s = 1st1 = t - t sound =

v=s/t1=340m/

If the sound velocity standard is not, it can be brought into the calculation.

1。Known: v=10m s t=4 2s solution: s=vt=10m sx2s

200m200-(10*4)=160m

A: When you hear the echo, the car is 160m away from the mountain in front of you

I'm sorry, I'll only write the previous one, sorry.

Students in the distance hear voices that are less loud.

The intensity of a sound is called loudness. Loudness is the strength of the sound judged by the senses, that is, the loudness of the sound, according to which it can arrange the sound in a sequence from light to loud. The magnitude of loudness is mainly dependent on the intensity of the sound and is also related to the amplitude of the sound.

The greater the amplitude, the greater the loudness; The lower the amplitude, the less loudness. In addition, loudness is also related to the distance from the emitter, and the closer to the emitter, the louder it becomes.

2.First empty: ABC

Second empty: gh

Third empty: AD

Fourth space: Adjust the tightness of the strings.

Hit the drum with a small vertical to make a sound, and put the ping pong ball on it, you can see the ping pong ball bouncing up and down, indicating that the occurrence of the object needs to vibrate.

2.Put the 2 3 of the steel ruler on the exposed desktop, and the remaining 1 3 press the exposed desktop part with your hand to press down different amplitudes, and listen to its sound after letting go, indicating that the greater the amplitude, the louder the sound.

(1) (3) Choose a string of suitable length, pluck the string vigorously, feel the pitch of the string, and then tighten the string appropriately, pluck the string with the same force, feel the pitch of the string again, and compare the pitch of the string before and after.

1) Selected equipment: steel ruler and wooden comb.

2) The main experimental procedure: take a steel ruler and use different forces to swipe over the teeth of the wooden comb, and listen to the sound made by each wooden comb.

3) The physics you designed to illustrate is that the pitch of a sound is related to frequency (I hope it helps you, and I hope you can!). )

Question 1: aStudents in the distance hear voices that are less loud.

Question 2: In order to verify conjecture 1, the numbers (a) (b) (c) should be selected In order to verify conjecture 2, the numbers (c), (e), (g) should be selected In order to verify conjecture 3, fill in the missing data should be length 80 cross-sectional area.

As the experiment progressed, Xiaohua felt that the pitch of the strings might also be related to the tightness of the strings, and in order to verify this conjecture, the operations that had to be carried out were: (Adjust two or three strings with equal cross-sectional area or equal length to different tensions and then pluck them).

3. The following equipment is now given to you: a steel ruler, a wooden comb, a tuning fork, a table tennis ball (tied to a string), a rubber band, a drum, a paper, and a small hammer. Please design an experiment on acoustic phenomena with your choice of equipment.

1) Selected equipment: tuning fork, table tennis ball (tied with string), small hammer.

2) Main experimental steps:1Start by striking the tuning fork with a small hammer. 2.Touch the ping-pong ball tied to the string to the tuning fork that is making a sound. 3.See how the ping-pong ball (will bounce off).

3) The physics you are trying to illustrate in your experiment is that sound is produced by vibrations.

The third question is a tuning fork, a table tennis ball and a tether, a small hammer. A person puts a table tennis ball on top of this fork and hits the tuning fork with a small hammer, and he will see that the table tennis ball will move, indicating that the sound cause can transmit wave energy.

Loudness refers to the size of the sound heard, the timbre is to distinguish the sound, the frequency affects the tone, the smaller the amplitude, the smaller the loudness, and here the main thing is the distance 2（1）abc adf（3）80 3.Drums, small hammers, paper Tear the paper into pieces and put it on the drum and hit the paper with a hammer, and the beating sound is generated by vibration.