Physics. Approximate Timeline. Students are expected to keep up with class work when absent.

Transcription

1 Physics Approximate Timeline Students are expected to keep up with class work when absent. CHAPTER 15 SOUND Day Plans for the day Assignments for the day Properties & Detection of Sound Assignment 15.0 o Sound Waves o Detection of Pressure Waves o Perceiving Sound the decibel scale Properties & Detection of Sound o The Doppler Effect Assignment 15.1 Read section(s) The Physics of Music o Sources of Sound o Resonance in Air Columns Open pipe resonators Closed pipe resonators 4 Lab/Demo Speed of Sound in Air The Physics of Music Assignment 15.2 o Resonance in Strings o Sound Quality o Beats 6 Review for Chapter 15 Test 7 Chapter 15 Test Read section(s) 16.1

2

3 Study Guide Chapter 15 Quizzes Quiz 15.1 Properties and Detection of Sound 1. A sound wave is a variation that is transmitted through matter. 2. What type of waves are sound waves? 3. Pitch is related to. 4. Loudness is related to. 5. The perceived change in frequency as a source of sound moves toward or away from the detector is called the (2 words). 6. The unit of measurement of sound level is the. 7. Solve problems involving the Doppler Effect. Quiz 15.2 The Physics of Music 8. In general a closed pipe will resonate when the length of the pipe is. 9. In general an open pipe will resonate when the length of the pips is. 10. Musical instruments never emit a single frequency when a single note is played. The note we hear is also the lowest frequency emitted. a. What term is used to describe the lowest frequency heard? b. What term is used for all of the other frequencies emitted? 11. Define the term beats.

4 Study Guide Chapter 15 Test At the completion of chapter 15 you should 1. Know the definitions of the following terms. a. Pitch b. Loudness c. Decibel d. Doppler Effect e. Fundamental f. Harmonics g. Dissonance h. Consonance i. Beat 2. Know that sound is a longitudinal wave and requires a medium to travel. 3. Know the speed of sound in air at 0ºC and at 20ºC. 4. Be able to define and explain the Doppler Effect. 5. Be able to solve Doppler effect problems 6. Be able to define and explain pitch and loudness. 7. Understand the decibel scale and its relation to pressure. 8. Know that sound is produced by a vibrating object. 9. Know the audible range of frequencies. 10. Understand resonance and how it relates to both open and closed pipe resonators. 11. Know what is meant by timbre. 12. Understand the relationship between frequency and beats. 13. Understand the relationship between frequency and octaves on a musical scale.

5 Assignment 15.0 Vocabulary Define each of the following terms. 1. Sound Wave 2. Pitch 3. Loudness 4. Sound Level 5. Decibel 6. Doppler Effect 7. Closed-Pipe Resonator 8. Open-Pipe Resonator 9. Fundamental 10. Harmonics

6 11. Dissonance 12. Consonance 13. Beat

7 Assignment 15.1 Properties & Detection of Sound Short Answer: Answer each question in the space provided. Write or print clearly. IF I CAN T READ IT, IT S WRONG. 1. When timing the 100 m run, officials at the finish line are instructed to start their stopwatches at the sight of smoke from the starter s pistol and not at the sound of its firing. A) Explain. B) What would happen to the times for the runners if the timing started when sound was heard? 2. Does the Doppler shift occur for only some types of waves or for all types of waves? 3. Sound waves with frequencies higher than can be heard by humans, called ultrasound, can be transmitted through the human body. A) How could ultrasound be used to measure the speed of blood flowing in veins or arteries? B) Explain how the waves change to make this measurement possible. 4. The speed of sound increases by about 0.6 m/s for each degree Celsius when the air temperature rises. For a given sound, as the temperature increases, what happens to the following? A) the frequency B) the wavelength

8 5. In a science fiction movie, a satellite blows up. The crew of a nearby ship immediately hears and sees the explosion. If you had been hired as an advisor, what two physics errors would you have noticed and corrected? 6. If the pitch of sound is increased, what are the changes in the following? A) the frequency B) the wavelength C) the wave velocity D) the amplitude of the wave Problems: Solve each of the following problems. Show all work. Circle your answer expressed with the correct number of significant figures and units. 7. You hear the sound of the firing of a distant cannon 5.0 s after seeing the flash. How far are you from the cannon? 8. If you shout across a canyon and hear an echo 3.0 s later, how wide is the canyon?

9 9. A sound wave has a frequency of 4700 Hz and travels along a steel rod. If the distance between compressions, or regions of high pressure, is 1.1 m, what is the speed of the wave? 10. Sound with a frequency of Hz travels through water at 25ºC. Find the sound s wavelength in water. Do not confuse sound waves moving through water with surface waves moving through water. 11. If the wavelengths of a 4.40 x 10 2 Hz sound in fresh water is 3.30 m, what is the speed of sound in freshwater? 12. A rock band plays at an 80 db sound level. How many times greater is the sound pressure from another rock band playing at each of the following sound levels? A) 100 db B) 120 db

10 13. A baseball fan on a warm summer day (30ºC) sits in the bleachers 152 m away from home plate. A) What is the speed of sound in air at 30ºC? B) How long after seeing the ball hit the bat does the fan hear the crack of the bat? 14. Ultrasound with a frequency of 4.25 MHz can be used to produce images of the human body. If the speed of sound in the body is the same as in salt water, 1.50 km/s, what is the length of a 4.25 MHz pressure wave in the body? 15. A fire truck is moving at 35 m/s, and a car in front of the truck is moving in the same direction at 15 m/s. If a 327 Hz siren blares from the truck, what frequency is hear by the driver of the car?

11 16. A train moving at 31.0 m/s toward an observer blows a 305 Hz whistle. What frequency is detected on each of the following? A) A stationary observer. B) An observer moving toward the first train at 21.0 m/s. 17. The train in the previous problem is moving away from the detector. What frequency is now detected on each of the following? A) a stationary train. B) a train moving away from the first train at 21.0 m/s

12

13 Assignment 15.2 The Physics of Music Short Answer: Answer each question in the space provided. Write or print clearly. IF I CAN T READ IT, IT S WRONG. 1. What is necessary for the production and transmission of sound? 2. How can a certain note sung by an opera singer cause a crystal glass to shatter? 3. Why don t most musical instruments sound like tuning forks? 4. What property distinguishes notes played on both a trumpet and a clarinet if they have the same pitch and loudness? 5. Two flutists are tuning up. If the conductor hears the beat frequency increasing, are the two flute frequencies getting closer together or farther apart? 6. A covered organ pipe plays a certain note. If the cover is removed to make it an open pipe, is the pitch increased or decreased? Problems: Solve each of the following problems. Show all work. Circle your answer expressed with the correct number of significant figures and units. 7. One tuning fork has a 445 Hz pitch. When a second tuning fork is struck, beat notes occur with a frequency of 3 Hz. What are the two possible frequencies of the second fork?