Well wishers help to do a few physics problems, and a physics problem asks for a well wisher

1."Lightning fast"It refers to the measures that people naturally take (open their mouths wide to block their ears) when a sudden loud noise comes, so as to reduce the harm caused by noise.

2.Why do male cicadas chirp? Using the analogy of human occurrence, guess the vocalization of cicadas. (Answer the question).

Male cicadas have vocalizers on their abdomen, while females do not have vocalitizers.

The voice of the male cicada is made by the first.

The contraction movement of the generator in the first and second abdominal segments is sent out by forcing the membrane to vibrate on both sides. The dorsal flap (i.e., the "tympan cover") and the tympanum formed above the vocal membrane, as well as the two symmetrical abdominal valves (i.e., the "sound cap") and the left and right abdominal vents below have the functions of tuning and amplification, and the upper part of the abdominal chamber wall is an approximately white pleated membrane, and the lower half is an inverted and nearly translucent auditory membrane, which is as transparent as a mirror, so it is called "mirror membrane". The pleats, mirrors, and abdominal wall membranes of male cicadas are the auditory membranes that receive sound waves and the radiation membranes that sing sounds.

3.Give an example of how time it takes for sound to travel. (Answer the question).

Echo. 4.What physical quantities do you need to know to measure the length of a long steel pipe with acoustic knowledge? What instruments are needed? What physical quantities are measured?

time, the speed at which sound travels in a solid; Measure time with a stopwatch.

Using the formula s=vt, you can know the length of the pipe!!

Hee-hee......Extra points!!

Mouth. Shake.

The sports will start the pistol. Manure.

1. Reduce noise at the human ear.

2. I don't know.

3. When thunder, you only hear thunder after seeing lightning.

4. I don't know.

1.Prevent noise from getting into your ears (covering your ears).

2.Xiong Chan has a generator on her chest.

3.You stand on the mountain. Shout out down the mountain. An echo is heard.

4.Didn't learn.

1. Cut off the route of transmission.

2. Courtship. Sound is emitted by the vibration of the sounding membrane.

3 On a thunderstorm day, you will see lightning first, and then you will hear thunder.

4. You have to check the book first to know the wave production velocity v of the sound in the steel pipe

The propagation time of the sound as measured by the stopwatch is t s=vt

1 weakened at the receiving.

2. The cicada's voice vibrates by its wings.

3. When it rains, lightning is seen, and thunder is heard.

Cover your ears. Vibrating sounds.

In general, sound travels through the air at a speed of 340 meters per second.

time, the speed at which sound travels in a solid; Measure time with a stopwatch.

Open your mouth wide to block your ears.

Attract female cicadas to vibrate their wings.

Lightning is seen first and thunder is heard.

The speed at which sound travels in the steel pipe propagation time. Stopwatch.

1 Self-instinctive protection.

2 Because the cicada has a diaphragm, the diaphragm vibrates to make sound. Human vocalization is the vibration of the vocal cords, while cicada vocalization is the vibration of the diaphragm, and the sound is emitted by vibration, and then the medium is needed to transmit the vibration.

3.Echo. 4.The length of the steel pipe is l, the speed of sound propagation in steel v, and the propagation time of sound in steel t. Stopwatch.

Isn't that a question for the first year of junior high school?

1. Prevent noise from entering the ears.

2. Abdominal diaphragm vibrates.

3. When thunder strikes, you see lightning first and then hear thunder.

4. Know V (speed of sound) and T (time).

Measuring tools Stopwatch.

Formula s=v*t

Knee-jerk reaction; Attract female cicadas humans: vocal cord vibrations;

lightning and thunder;

The speed of sound of steel length of time.

Clock stopwatch. The speed of sound in steel, the speed of sound in the air, the time difference between the two sounds heard.

1 Conditioned reflex protection.

2 Attract female cicadas, and a voice comes with a mouth.

3 thunderbolts 4 sound in the steel pipe speed, stop watch, time.

The first one was in junior high school, but I can't remember it clearly, but it seems that it is to prevent noise from entering the ears (covering the ears), that is, to reduce the source of acceptance, and the second seems to be the vibration of the human vocal cords.

The third one I started the race from the smoke, not waiting for the gunshot, then it must be slower and the fourth one knew the density of the steel, the diameter, the speed of sound in the air at the same temperature, the stopwatch, the time difference.

The wind was blowing from west to east, and the speed of the wind was the same as the speed at which he was running.

It seems to be based on junior high school knowledge, and there is such a name.

Relative motion. of, frame of reference.

When using him as a reference, he should be regarded as stationary, and relative to the second object, such as the ground, at this time the ground is backwards, and this is the reason for the choice of reference, understand!

The wind speed is 18km h!The direction is from west to east! Because it is in a vertical falling state. So it's relatively static! So it's the same speed as Li Ming!

I can't see your diagram, I drew a diagram for your reference.

There's no picture, how do you know...

Forest resources are one of the most important resources on the earth, is the basis of biological diversity, it can not only provide a variety of valuable wood and raw materials for production and life, can provide a variety of items for human economic life, more importantly, forests can regulate the climate, maintain water and soil, prevent and mitigate natural disasters such as drought and flood, sandstorms, hailstorms; There are also functions such as purifying the air and eliminating noise; At the same time, the forest is also a natural botanical and botanical garden, feeding all kinds of birds and animals, and growing a variety of precious forest trees and medicinal materials. Forests can be renewed, are renewable natural resources, and are also an intangible environmental resource and a potential "green energy". The main indicators reflecting the quantity of forest resources are forest area and forest stock.

At present, most hair dryers cannot blow cold air, because of the voltage reduction with heating wires, there are only two specific circuits of strong heat and low heat, which are at least divided into three.

The heating wire is divided into three sections, four heads, the shortest is 12 24V, the top is connected to the full power, and the top is the small power.

The heating wire is divided into two sections, the short distance is connected to the motor, the full-wave power supply is full power, and the half-wave power supply is half-power (diode rectification).

There are two kinds of heating wires, high-resistance string motors, low-resistance heating, with full half-wave control power only the motor is 220V, which can work separately and send cool breeze.

Okay, I'll admit I'm talking nonsense, but I'm looking it up, and you know how it works, but I can't do it at all.

s1=20m*9+5m*10=230m

s=s1+s2=230m+150m=380mv=36km/h=10m/s

t=s/v=38s

A = V ta Truck: A Sedan = 1:6

108km/h=30m/s

a=30m/s/10s=3m/s2

40m/s/8s=5m/s2

10m s*2 Min Jean.

a=v1-v0 t=4m s-2m s 3s=2 Douzhi 3m s2a acceleration = 2 3

v=2/3*(3+9)=8

a deceleration = 8 4 = 2

s deceleration = 8 2 * 4 = 16

s acceleration = 8 2 * 12 = 48

s=16+48=64m, about how many floors to live on, think for yourself.

m s2 is the unit of acceleration I didn't write the unit in question 5.

If you don't understand it, you can say it

I'm looking for another question that looks a lot like yours.

The supply voltage is constant, r2 = 60When the switch S is disconnected, the indication of the ammeter is; When S is closed, the indication of the ammeter is to find the resistance of R1.

You should be able to write.