Classical exercises for physics and sound in the second year of junior high school

Let the distance between people and the two sides of the cliff be x, y (you may wish to set x>y) from the question: 2x-2y) 340=5

x+y=1200

Twitch Factory Majesty Broken Pile Bidding Coupon Bowl Cunning Solution Calendar Thing De Ant Tour X Limb Scatter 1025, Y 175

b.A sound caused by the vibration of the surrounding air when the ball skin breaks.

b. Block the propagation of noise.

c. The incense burns to increase the temperature of the bell, the material structure of the bell changes, and the frequency of the bell vibration changes the familiar timbre.

Deafening loudness.

Closing the eyes and plugging the ears is the way to reduce noise at the human ear.

It feels quiet in the woods because the trees are able to reduce the noise and not make a sound from the way it travels.

。Deafening.

5.The leaves in the woods are soundproof, and it is difficult for sound waves to be conducted.

6.The walls are made of sound-absorbing materials, and the various components are muffled and the structure of the house is changed to reflect as little sound waves as possible.

b b a 1 sound can travel through the air 2 loud 3 reduce noise from the human ear trees can absorb sound waves to prevent sound propagation sound insulation materials are used.

Each voice in the BBC has its own silver color.

Loudness attenuates noise at the human ear.

Trees can attenuate sound.

Communicate with cardboard.

1."Place one end of the metal rod against the machine and the other end close to the ear, so that you can hear whether some parts of the machine are normal"The scientific argument that sound travels in solids and loses less energy than in air.

2.This is judged by the pitch of the sound heard. Because the sound produced during filling is the result of the vibration of the air column inside the bottle, the shorter the air column, the higher the tone. When the water level is high enough to produce a specific tone of sound, it indicates that the water is almost full.

1. Solid metal can be used as a sound propagation medium.

2. Liquid can be used as a sound propagation medium.

1. The timbre is different.

2.The timbre is different.

1. Solid propagation sound is better than airborne sound.

2. The air column in the bottle is vibrating, the higher the tone, the shorter the air column, indicating that it is full.

1. Sound propagates best in solids.

2. Different tones (when the water is just poured, the air column in the pot is long and the tone is low; When it is almost full, the air column in the pot is short and the tone is high).

1: Determine whether the timbre is correct.

2: The shorter the air column, the higher the pitch, and the longer the air column, the lower the pitch.

1.Sound waves can carry information 2The water column in the water bottle transmits sound.

The timbre is different, please see the corresponding chapter of the physics textbook, the explanation is very clear.

1.(1) Stay away from the mountains.

The sum of the distance traveled by the car and the sound in the time between the time the horn is sounded and the echo is equal to twice the distance from the horn to the mountain (the analysis process can be omitted).

t*(v sound + v car) = 2*s (list relation).

2s*340m s+2s*v car = 2*360m (data carry-in).

V-car = 20m s (the calculation step can be omitted).

2) The distance between the car and the mountain before the horn is equal to the difference between the distance from the mountain and the distance covered by the car when the echo is heard.

s-t*v-car=s'

360m-2s*20m/s=s'

s'=320m

2.(1) (The next analysis may directly substitute the data) When car B hears it, the distance between the two cars is equal to the distance difference between the sound and train A in 5 seconds, that is, s=5s*(v sound-v car) (because the speed of the two is the same, it is uniformly set to v car).

After another 40s they meet, so s = 40s * (v car + v car).

5s*(340m s-v car) = 40s * 2 * v car.

V-car = 20m s

2) The distance between the two cars before the horn is equal to the distance traveled by the sound within 5 seconds and the distance traveled by car B within 5 seconds.

5s(340m/s+20m/s)=1800m

I won't draw the picture, you try to draw it yourself according to the analysis, understand the relationship between quantities, and this kind of problem is much simpler).

1 (1) The speed of sound we know is 340m s, the sound has gone 340 * 2 = 680 meters in two seconds, assuming that the speed of the car is v, the car has traveled the distance of s = 2v in 2s, and the two distances add up to twice the distance of the car from the mountain at this time, so 2v + 680 = 360 * 2 (where 2 means twice); v=20m/s

2）360-20*2=320m。

2. (1) 5s, the sound has walked 340 * 5 = 1700m, car B has walked through 5v, 40s, and the two lathes have walked 40v * 2 distance, so 80v + 5v = 1700, v = 20m s (2) the distance between the two workshops is 90v = 1800m.

It's not easy to upload, so draw it yourself.

Solution: S sound = V empty t = 340m sx2s = 680ms distance = (s sound + s car) 2

360 = (680 + 2v car) 2

V car = 20m s, S car = V car t = 40m

S Ming = S distance - S car = 360m-40m = 320m Answer: 20m s, 320m

It's very simple to list a binary equation.

The topic is not difficult, and the upstairs is all the right solution.