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Module 14
Module 14
| Question | Answer |
|---|---|
| Transverse wave | A wave with a direction of propagation that is perpendicular to its direction of oscillation. |
| Longitudinal wave | A wave with a direction of propagation that is parallel to its direction of oscillation. |
| Supersonic speed | Any speed that is faster than the speed of sound in the substance of interest |
| Sonic boom | The sound produced as a result of an object traveling at or above Mach 1 |
| Pitch | An indication of how high or low a sound is, which is primarily determined by the frequency of the sound wave. |
| To adjust a horn on a car if the pitch is too low what should the engineers change the electronics so as to produce sound waves with longer or shorter wavelengths? | need to adjust the electronics to emit sound waves with a shorter wavelength. |
| #3. A sound wave is traveling through air with a temp of 30 degrees C. What is the speed of the sound wave? | Equation 10.2 v = (331.5 + 0.6 x 30) m/sec v = (331.5 + 18) m/sec v = 349.5 m/sec |
| #4. If the sound wave in problem 3 has a wavelength of 0.5 meters, what is its frequency? | Use equation 14.1 f = v/wave length f = 3495m/sec / 0.5 m = 699 1/sec The frequency is 699 Hz. |
| #5. A sound wave has a speed of 345 m/sec and a wavelength of 500 meters. Is this wave infrasonic, sonic or ultrasonic? | Infrasonic waves have freq less than 20 Hz. Ultrasonic more than 20,000 Hz and sonic waves bet 20 and 20,000 Hz. Determine frequency. Equation 14.1 use - f = v/wavelength = 345 m/sec / 500 m = 0.69 1/sec Since the frequency is less than 20 Hz - infraso |
| #6.A physicist takes an alarm clock and puts it in an airtight chamber. Sealed but still full of air, the physicist is able to hear alarm outside of the chamber. If the physicist then uses a vacuum pump to evacuate air, will he be able to hear alarm? | The physicist will not be able to hear the alarm because, without air, the sound waves from the alarm have nothing through which to travel. Thus, they cannot make waves. As a result, there is no sound. |
| #7. Are sound waves transverse waves or longitudinal waves? | Sound waves are longitudinal waves. |
| #8. You are watching lightning. You see lightning and 2.3 seconds later you hear thunder. How far away did the lightning strike? The temperature at that time is 13 degrees C. | Use time diff between lightning and sound. First, speed of sound: v = (331.5 + 0.6 x 13) m/s v = (331.5 + 7.8) m/s v = 339.3 m/sec Then equation 14.3 Distance traveled = (speed) x (time traveled) distance traveled = (339.3 m/sec) x (2.3 sec) = 780.3 |
| #9. Sound waves are traveling through the air and suddenly run into a wall. As the sound waves travel through the wall, do they travel faster, slower, or at the same speed as when they were traveling in the air? | Sound travels faster in solids than it does in gases or liquids. Thus, the sound travels faster in the wall. |
| #10. In the situation in #9, what happens to the amplitude of the wave? Is the amplitude of the wave smaller, larger, or the same as the amplitude before the wave hit the wall? | When a wave strikes an obstacle, part of the wave is reflected and part is transmitted through it. Thus, only a portion of the wave actually goes through wall. The amplitude of the wave will be smaller. |
| #11. A jet aircraft is traveling at Mach 2.5 through air at 1 degrees C. What is the jet's speed in m/sec? | Speed of sound v = (331.5 + 0.6 x T) m/sec v = (3331.5 + 0.6 x 1) m/sec v = (331.5 + 0.6) m/sec = 332.1 m/sec Since sound travels at 332.1 m/sec, Mach 2.5 is 2.5 x (332.1 m/sec), or 830.25 m/sec. Then - 464.1 / 331.5 = 1.4 - jet traveling at Mach 1 |
| #13. Why do jets travel at speeds of Mach 1 or higher only in sparsely populated regions? | When a jet travels at Mach 1 or higher, it creates a shock wave of air that causes a very loud boom. This boom can damage people's ears and building. |
| #14. A guitar player is plucking on a string. If he takes his finger and pinches the string of the neck of the guitar so as to shorten the length of the string, will the pitch of the sound emitted increase, decrease, or stay the same? | Since the string becomes shorter, the wavelength will be smaller. This will result in a higher frequency. Thus, the pitch will increase. |
| #15. You hear two musical notes. They both have the same pitch, but the first is louder than the second. If you compare the sound waves or each sound, what aspect(s) of the wave (wavelength, frequency, speed, and amplitude) would be the same? What diff? | The wavelength, frequency, and speed will all be the same. After all, the pitch is determined by the frequency, which, in turn, determines the wavelength. The speed depends only on the temp. The amplitudes of the waves will be different. |
| #16. The horn on your neighbor's car is stuck, so it is constantly blaring. You watch your neighbor get into the car and drive away. Compare the pitch of the horn before he starts to drive away to the pitch you hear as he is driving away. | As the car travels away, the sound waves that are produced by the horn get farther and farther apart. This makes the wavelength seem longer to your ears, which will result in a lower frequency. The horn's pitch is lower when it is moving away from you. |
| #17. You are riding your bicycle toward a stationary police car with a siren that is blaring away. Will the pitch of the siren sound lower, higher, or the same as it will sound when you actually stop your bicycle? (Assume the actual pitch is constant) | As you travel towards the police car, you will encounter the compressions of the sound waves faster than when you stand still. As a result, the wavelength will seem shorter to you, which will produce higher frequencies. So, the pitch will get higher. |
| #18. You are near a hwy trying to talk on the pay hpone. You have raised your voice because of the noise. Your voice is about 80 decibels. Traffic is 100 decibels. How many times larger is the intensity of the traffic's sound waves as compared to yours? | Figure bel units traffic sound vs. voice. 80 decibels/1 times 0.1 bel/1 decibel = 8 bels 100 decibels/1 times 0.1 bel/1 decibel - 10 bels Traffic is 2 bels louder - increase in sound is 2 factors of ten higher. Traffic 10x10= 100 times larger than voic |
| #19 An amplifier can magnify the intensity of sound waves by a factor of 1,000. If a 30-decibel sound is fed into the amplifier, how many decibels will come out? | 30 decibels/1 times 0.1 bel/1 decibel = 3 bels If amplifier magnifies the intensities of the waves by a factor of 1,000, that's the same as 10x10x10. 3 bels larger. So, 6 bels, which is 60 decibels. |
Created by:
davisjuring
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