# How the Circular Saw Sounds Vary

### Transcript

1 Examination 3 physics 9 grade “Mechanical vibrations and sound. Sound” Option 1 1. Why do the windows rattle in the bus at a certain engine speed? 2. Why are the sounds heard in the fog at a farther distance than in sunny weather? 3. The distance between the crests of the waves in the sea is 5 m. With the oncoming movement of the boat, the wave hits the hull of the boat 4 times in 1 s, and 2 times with the incidental one. Find the speed of the wave and the boat, if you know that the speed of the boat is greater than the speed of the wave. 4.How does the pitch of the string or tuning fork change with increasing temperature? 5. The frequency range of the piano is from 90 to 9000 Hz. Find the wavelength range of the piano sound in the air. Option 2 1. Why don’t bats stumble upon obstacles even in total darkness? 2. Why are the speakers speaking in the city square speaking slowly, separating the word from the word for a long pause? 3. A man standing on the seashore determined that the distance between successive crests was 12 m. In addition, he calculated that 16 wave crests had passed past 75 with him. Determine the speed of wave propagation. 4. Can the sound of a strong explosion on the moon be heard on Earth? 5. What is the depth of the sea if the ultrasound sent and reflected from the seabed returned to the surface after 0.9 s? The speed of sound in water is 1480 m. Option 3 1. Will the pilot hear the sound of a jet engine if the plane is flying at supersonic speed and the engine is behind the pilot? 2. If you carry buckets on the beam, then at a certain pace of walking, they begin to sway greatly. How to explain this phenomenon? How to reduce the swing of buckets? 3. The wings of a bee oscillate with a frequency of 240 Hz. How many wings can a bee make when it reaches a flower field located at a distance of 500 m if it flies at a speed of 4 m / s? 4. When small sea waves approach an inclined coast, foamy ridges form on them. Why? 5. Who flies faster in flight: a fly, a bumblebee or a mosquito? How can this be determined? Option 4

2 1. Find the amplitude, period and frequency of body vibrations according to the graph in the figure. 2.Why are bass strings wrapped with metal wire? 3. During a thunderstorm, a person heard thunder 15 seconds after a flash of lightning. How far has the discharge occurred from it? 4. The voice is heard at a great distance, but sometimes words cannot be made out. What is the reason for this? 5. In the oceans, the wavelength reaches 300 m, and the period is 13.5 s. Determine the propagation velocity of such a wave. Option 5 1. What should be done with the pendulum of the clock if it is in a hurry? 2. Why, regardless of the direction of the wind, the waves roll onto a gentle shore at an angle close to a straight line? 3. When the observer perceives by sound that the plane is at its zenith, he sees it at an angle of 73 0 to the horizon. How fast does a plane fly? 4. Why does an incomplete kettle make a louder noise before boiling water than a full one? 5. As a result of the explosion made by geologists, a wave propagated in the earth’s crust at a speed of 5 km / s. Reflected from the deep layers of the Earth, the wave was recorded 22 s after the explosion. At what depth does the rock lie, which differs sharply in density from the earth’s crust? Option 6 1. On the surface of the water in the lake, the wave propagates at a speed of 6 m / s. What is the period and frequency of the buoy oscillations if the wavelength is 3 m? 2. If you put a wooden circle on the water in the bucket, then when walking the water does not splash. Why? 3. How can bats with poor eyesight find mosquitoes or other flying insects in the dark? 4. If you hit with a hammer on one end of a long metal pipe, then standing at the other end of the pipe will hear a double blow. Why? 5. The approaching boat gave a beep, the sound of which was heard on the bridge after 3 seconds. After 3 minutes, the ship passed under the bridge. Air temperature 0 0 С. Find the speed of the ship. Option 7

3 1. Why is the hollow body of the violin made curly? 2. What effect do curtains and upholstered furniture have on hearing? 3. The wings of a bee flying after nectar fluctuate with a frequency of 420 Hz, and when flying back (with nectar) 300 Hz. Bee flies behind nectar at a speed of 7 m / s, and back at a speed of 6 m / s. When flying in which direction and by how much more will a bee make wings with wings if the distance from the hive to the flower field is 500 m? 4. Sea waves, approaching the coast, increase height, sometimes reaching 50 m. Why is this happening? 5. Why are bass strings wrapped with metal wire? Option 8 1. Does the temperature change affect the accuracy of the pendulum clock? 2. In a traveling wave, particle A has the direction indicated in the figure. In what direction does the wave “move”? 3. Rybolov noticed that in 10 s the float made 20 oscillations on the waves, and the distance between adjacent humps of waves is 1.2 m. What is the speed of wave propagation? 4.Can echoes occur in the steppe? 5. At a certain speed of rotation of the sewing machine, the table on which it stands sometimes swings violently. Why? Option 9 1. When they listen to distant noise, they involuntarily open their mouths. Why? 2. If we look from a distance at the soldiers marching to the brass band, then it seems to us that they are not in tune with the music. Why? 3. On the lake in calm weather, a heavy anchor was dropped from a boat. Waves started from the throwing place. A fisherman, standing on the shore, noticed that the wave reached him after 50 s, the distance between the neighboring humps of the waves was 0.5 m, and after 5 s there were 20 bursts on the shore. How far was the boat from the shore? 4. Why, with a constant wind, sometimes very large waves arise, according to marine custom, called the “ninth rampart”? 5. At what distance from the observer lightning flashed if he heard thunder 6 seconds after he saw the lightning?

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4 Option 10 1. How does the wave size on the lake change with increasing wind speed? 2. Why does the door only slightly open in a noisy corridor, practically does not reduce noise? 3. At what maximum speed of a train can a resonance of vertical oscillations occur due to periodic wheel shocks at the rail joints, if the rail length between the joints is 25 m, and the period of the car’s own vibrations is approximately 1.25 s? 4.Accidentally, flying into the window, the bat often sits on people’s heads. Why? 5. Will the pitch of the straight pipe change if it is bent? Option 11 1. Why, listening to a high-quality recording of his voice, a person does not recognize it? 2.At a height of more than 3 km from the surface of the Earth, it is impossible to perceive a single sound whose source is on the surface of the Earth. Why? 3. For 1 s, the mosquito makes 600 wings flapping, and the period of oscillation of the bee’s wings is 3 ms. Which of the insects and how much will make a greater number of strokes per minute during flight? 4. Why don’t we hear the echo in the room? 5. The hero of one of O. Henry’s stories hit the piglet with such force that he flew, “ahead of the sound of his own screech.” What is the lowest speed a pig would have to fly in order for the described case to actually happen? Option 12 1. Why is there a sharp deafening blow with a near thunderstorm, and with a distant thunder? 2. The pitch of the circular saw decreases when the board is pressed against the saw. Why? 3. The distance to the obstacle reflecting the sound is 68 m. After how long does a person hear an echo? 4. What car shakes less in empty or loaded? Why? 5. A military signal rocket launched vertically upward exploded 5 seconds after launch, and the sound of a gap was heard 0.4 seconds after the gap. At what height and at what average speed did the rocket rise? Air temperature 0 0 С. Option 13 1. There are only four strings on the violin. However, with the help of these few strings, the musician receives a huge number of very diverse sounds. How it’s done? 2. Can astronauts communicate with each other when they enter outer space using sound speech?

5 3. The plane flies horizontally at an altitude of 4 km above the Earth’s surface with supersonic speed. The sound reached the observer 10 seconds after the plane flew over it. Determine the speed of the aircraft. 4. If you make a sound in front of an open piano, then the piano starts to sound when you press the pedal. How to explain this? 5. What is the depth of the sea if the ultrasound sent and reflected from the seabed returned to the surface after 0.9 s? Option 14 1. Is it possible to swing a heavy swing, applying very little effort to them, and get a large amplitude of oscillation of these swings? 2. Why, when checking the wheels of cars during a train stop, they are tapped with a hammer? 3.How does the sound wavelength change when moving from air to water, if the speed of sound propagation in air is 340 m / s, and in water 1480 m / s? 4. If you hold a wet finger on the glass, you get a sound. Why? 5. Does a military pilot hear the sound of a jet engine if the plane is flying at supersonic speed and the engine is behind the pilot? Option 15 1. When the plane flies at subsonic speed, the noise of its engines is heard on the ground. If the plane flies at a supersonic speed, then first a loud pop is heard, and then the noise of the engines. What is the reason for this? 2. Are sea waves longitudinal or transverse? 3. When measuring the depth of the sea under the ship with the help of an echo sounder, it turned out that the moments of departure and reception of ultrasound are separated by a time interval of 0.6 s. What is the depth of the sea under the ship? 4. Why in the mountains echo multiple? 5. The amplitude of the vibration of the point of the string is 1 mm, the frequency is 1 kHz. Which way does the point go in 0.3 s? Option 16 1. Will the swing period fluctuate if, instead of one person, two sit on the swing? 2. When small sea waves approach an inclined coast, foamy ridges form on them. Why? 3. Who flies more often in flight: a fly or a mosquito? Explain the answer. 4. The sound of an explosion made in the water near the surface, the devices installed on the ship and receiving sound through the water, recorded 45 s earlier than it came through the air. At what distance from the ship did the explosion occur? The speed of sound in water is 1540 m / s, in air 340 m / s.

## How the Circular Saw Sounds Vary

6 5. To be heard, we scream and at the same time put our hands to our mouths. Why are we doing this? Option 17 1. Why is it difficult to determine where the sound comes from in the forest? 2. It has been established that a bee flying with a bribe (flower juice collected by it) into the hive flies its wings on average 300 times per second, and unloaded about 440 times per second. Explain how experienced beekeepers know by the buzzing of bees whether they fly for prey or return home. 3.How will the oscillation period of the pendulum change if it is transferred from air to water or into a viscous oil? 4. The boat is swinging on waves propagating at a speed of 15 m / s. The distance between the two nearest crests of the waves is 6 m. Determine the period of oscillation of the boat. 5.Why do they rub the bow before the game with rosin? Option 18 1. Will the oscillation hours of the walking clocks be preserved if they are transferred from the Earth to the Moon? 2. The judge of the race walking competition is at the finish. When should he launch his stopwatch: when will he see the smoke of a starting pistol or will he hear a shot? Explain the answer. 3. Is the saying true: “He is like a fish”? 4. The motorcyclist, moving along a straight section of the road, saw a man standing on the road hit with a rod on a hanging rail, and after 2 seconds he heard the sound of an impact. What speed did the motorcyclist move if he passed a man 36 seconds after the start of observation? 5. The length of the sound wave in the air for the lowest male voice is 4.3 m, and for the highest female voice 25 cm. Find the vibration frequencies of these voices. Option 19 1. How to distinguish by ear, the electric drill is idling or drilling a hole? 2. Why do not we perceive as sound those air vibrations that are created by the wings of a flying bird? 3. In the oceans, the wavelength reaches 300 m, and the period is 13.5 s. Determine the propagation velocity of such a wave. 4. A stone is thrown into the river. What will be the formed wave: round or elongated current? 5. The sound of an artillery shot reached one observer after 3 seconds and the other after 4.5 seconds after the flash of a shot. The distance between the observers on the front is 1 km. Air temperature 0 0 С. How to determine the location of the gun, if the locations of the observers are known? Option 20

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7 1. Why are coniferous and deciduous forests noisy from the wind in different ways? 2. Why are all the vibrating installations of tall buildings placed on special rubber or metal shock absorbers? 3. Why is the prompter booth lined with felt? 4. The distance between the two railway stations is 8.3 km. How long does sound travel from one station to another through the air? On the rails? Air temperature 0 C. The average speed of sound propagation in steel is 5500 m / s. 5. Over the past years, a lot of cases of bird collisions with turboprops and turbojets have been recorded. Sometimes it happens that birds simply “attack” airports. How can this be explained? Option 21 1. How does sound occur when chirping crickets? 2. A fisherman who lived near the mouth of a river flowing into the ocean moved to a new place of residence a few kilometers upstream. To his surprise, he found that the time between the beginning of the ebb and the beginning of the ebb decreased, and the time between the beginning of the ebb and the beginning of the ebb increased. How can this be explained? 3.There are sinks in which noise is heard if they are applied to the ear. Sometimes the same noise can be heard by bringing a glass opening to your ear. Give an explanation. 4. A tube 0.5 m long is closed at one end. Determine the natural frequency of air oscillations in the tube at a temperature of 15 0 C. 5. How can astronauts talk on the moon? Option 22 1. Can a projectile fired from a gun outrun the sound of a shot? 2. How do I move the lentil of the pendulum when the clock is behind? 3. Bats’ vision is known to be very poor, and they are guided only by an ultrasonic locator. With its help, mice surprisingly accurately determine the location of even the smallest insects and catch them on the fly without a miss. But sometimes there are failures. And usually with butterflies. Why doesn’t an ultrasonic bat locator always detect them? 4. It will determine the maximum and minimum length of sound waves perceived by a person. The speed of sound is 340 m / s, the cutoff frequencies are 20 Hz and Hz. 5. Why during thunderstorms are heard peals of thunder, and not just one blow? Option 23 1. When selling porcelain or glassware, the seller taps the product with a pencil. Why is this done?

8 2. Can an astronaut hear the sound of a meteorite falling on the moon? 3.How will the pendulum clock change during the onset of hot summer days compared to cold winter days if the clock is installed in an uninsulated room (metal pendulum rod)? 4. The frequency of the tuning fork 440 Hz. What is the length of the sound wave propagating from the tuning fork in the air? In water? The speed of sound at 0 0 C in air is 332 m / s, and in water 1400 m / s. 5. Why does the music in the concert hall sound a little quieter than at its rehearsals? Option 24 1. At what distance from a steep cliff is a person if, clapping his hands, after 1 s he heard the echo of a pop? 2. There is a pendulum clock in the cabin of the passenger ship. How many oscillations will the pendulum make during a 800 km transition if the average speed of the vessel is 20 km / h and the oscillation frequency of the pendulum is 1 Hz? 3. A meteorite crashes into the moon. After what time will sensitive instruments on Earth record the sound of an explosion? 4. In the middle of the pond the ball floats. To drive him to the shore, the boy creates a pAL-KOI wave. Will he thus achieve the goal? 5. Why do we need boxes for tuning forks, cases for violins and guitars? Option 25 1. Crickets perceive sounds with a frequency of Hz, grasshoppers of Hz, locusts up to Hz. Determine the period of vibration perceived by these insects. 2. Hummingbirds fly at high speed and flap wings so quickly that the shape of the wing is invisible. The number of strokes can reach 20-25, and in some species up to 50 per second! Determine the wavelength that the hummingbird generates. 3. Tsunami. Huge sea waves appear as a result of earthquakes. The largest of them in the previous century had a height of 67 meters. What is the amplitude of particle oscillations of this wave? 4. Why sometimes, when performing opera arias, crystal chandeliers begin to ring? 5. Why, by changing the tension of the string, you can change the pitch of a musical instrument? Option 26 1. The height of the singer’s voice depends on the length and tension of the vocal cords. In men, the lengths of the vocal cords is mm. (bass 25 mm, tenor 18 m), in women mm. Frequency range corresponding to bass in men, Hz, baritone Hz, tenor Hz. Define a range of ox lengths corresponding to these voices.

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9 2. In what sequence should the ranges of audible sound, ultrasound and infrasound be placed on the wavelength scale? 3. A knock turns out louder if you knock not on the wall, but on the door with the same force. Why is this happening? 4. A huge mass of water falls Niagara falls from a height of 50 m. The noise of Niagara during the day is usually heard at a distance of 1.6-2 km, at night the range of its audibility can reach 6-7 km. How long does sound travel from Niagara at a distance of hearing? 5. Will oscillations of the ball mounted on the spring be possible if the entire system comes to zero gravity? Option 27 1. The frequency of voltage fluctuations in the electrical network is 50 Hz. Determine the period of oscillation. 2. The maximum or minimum acceleration at those times when the speed of the oscillating spring pendulum is 0? 3. One bat absorbs more than 700 mosquitoes within an hour. Ultrasonic signals with a frequency of kHz and a duration of 0.2-100 milliseconds, bats generate bats, generate larynx and emit through the mouth or nostrils. At what distance can a bat detect an insect or an obstruction? 4. Why do not we hear the roar of powerful processes taking place on the sun? 5. Determine the wavelength shown in the figure. What is the amplitude of particle oscillations in the wave? Option 28 1. Why is it easier to go in shoes with thick soles at a certain frequency of steps? Explain in terms of energy conversion. 2. When in 1815 on the island of Sumbawa, Indonesia, the Tambora volcano “spoke”, its “voice” was heard all over Java, in Kalimantan and in New Guinea, in Australia. On the coast of Sumatra, and it is four hundred and sixty kilometers from the volcano, its eruption was given by cannon cannon. How long did the sound go to the coast of Sumatra? Accept the speed of sound as 340 m / s. 3. The speed of the wings of different insects is different. So, for large butterflies, for example, a swallowtail, the number of swings per 1 second is 5, for locusts 18, for housefly 120, for bee 180, for gall midge Which of these insects will we hear?

10 4. Why do people talking in open areas speak louder than being at the same distance in the room? 5. What should be the gait of a girl carrying water on the beam so that she is less tired when walking? Option 29 1. How will the clock with the second pendulum installed for Moscow, at the pole and at the equator go? 2. Will the swing period change if the boy sways first while sitting and then standing? 3. The range of wavelengths of sound waves corresponding to the female voice of the contralto is cm, mezzosoprano cm, soprano cm, coloratura soprano see. Determine the frequency range corresponding to the female voices. The speed of sound in air is considered 340 m / s. 4.How does the sound occur when the bells hit? The weight of the bell tongue can reach 50 kg or more. How do you manage to swing it with just one ringer? 5. In the former Yugoslavia, one of the places near Kursumli was considered for a long time devilish. Stone figures created by the diligence of wind and moisture made various sounds at night, frightening superstitious people for whom these sounds were nothing more than devilish machinations. In Egypt, the remains of the ancient Karnak Temple sound in the mornings, at sunrise. Explain the origin of the sounds. Option 30 1. The minnows pick up sound at a distance of 30 meters. Determine the time after which the minnows hear the sound from the source, if the speed of sound in water at a temperature of 25 0 C is equal to 1500 m / s. 2. Many birds are equipped with ultrasonic “navigation devices. Echo sounders ”, but the most skilled navigators are fat goats, or guajaros. They make quiet clicking sounds, which are easily caught by the human ear. These sounds are reflected from the walls of the cave and other obstacles. After what time do the Kozodoi perceive the signal sent by them, if the distance to the obstacles in the cave where they live is 2-5 m? The speed of sound in the cave is considered equal to 330 m / s. 3.How will the period and vibration frequency of the elastic board mounted on the diving board change if a boy sways on the board after an adult, preparing to jump? 4. Does the temperature change affect the accuracy of the pendulum clock? 5. Can earthquakes be attributed to oscillatory motion?