0WAVES and SOUND Worksheet 1.When an automobile moves towards a listener, the sound of its horn seems relatively a. low pitched b. high pitched c. normal 2. When the automobile moves away from the listener, its horn seems a. low pitched b. high pitched c. normal 3. The changed pitch of the Doppler effect is due to changes in a. wave speed b. wave frequency 4. Circle the letter of each statement about the Doppler Effect that is true. a. It occurs when a wave source moves towards an observer. b. It occurs when an observer moves towards a wave source. c. It occurs when a wave source moves away from an observer. d. It occurs when an observer moves away from a wave source. 5. True / False: A moving wave source does not affect the frequency of the wave encountered by the observer. 6. True / False: A higher frequency results when a wave source moves towards an observer. 7. Two fire trucks with sirens on speed towards and away from an observer as shown below. a) Which truck produces a higher than normal siren frequency? b) Which truck produces a lower than normal siren frequency? 8. What is the frequency heard by a person driving at 15 m/s toward a blowing factory whistle (800. Hz) if the speed of sound is 340.6 m/s? 9. From the previous problem, what frequency would he hear after passing the factory if he continues at the same speed? 10. A car approaching a stationary observer emits 450. Hz from its horn. If the observer detects a frequency of 470. Hz, how fast is the car moving? The speed of sound is 343 m/s. 11. While standing near a railroad crossing, a person hears a distant train horn. According to the train's engineer, the frequency emitted by the horn is 440 Hz. The train is traveling at 20.0 m/s and the speed of sound is 346 m/s. a) What would be the frequency of the train's horn if the train were at rest? b) What is the adjusted frequency that reaches the bystander as the train approaches the crossing? c) What is the adjusted frequency that reaches the bystander once the train has passed the crossing? 12. Determine the speed of sound at 45.0 ºC. 13. A burglar alarm is wailing with a frequency of 1200. hertz. What frequency does a cop hear who is driving towards the alarm at a speed of 40.0 m/s? The air temperature is 35.0 ºC. 14. With reference to the previous problem, what frequency would the burglar hear, if he was running away from the alarm at a speed of 10 m/s? Since the vibrating object is moving across the tray. If you are standing on the sidewalk as the cop car approaches you at a speed of 15. Out in the ocean.6 m deep. A physics student sitting on the beach notices that a wave hits the beach every 5. What would that frequency be? The speed of sound is 343 m/s. but you measure the horn of the other car to be sounding at 600. You’re the driver of one of the cars. what frequency would you hear if the cop were driving away from you at a speed of 25 m/s? 17. As shown in the picture above (drawn actual size). you can find out what the frequency of the alarm would be if you had just held it in your hands. You. standing directly under it. In the previous problem. 18. You measure your car’s horn to be sounding at 512 Hz.2 m high meets a wave trough from another direction which is 2. An alarm clock is dropped off the edge of a tall building. the pattern of waves shows a Doppler effect and the wavelength (the distance between the ripples) is different in different directions. b) If the speed of water waves in this tray of water is 10. hear a tone of 1350. what frequency would you hear? The speed of sound is 343 m/s. a wave crest 3. What is the speed of these waves? 22.0 seconds.0 m tall. Hz coming from the clock at the instant it hits the ground. There were 4 nodes in the standing wave produced. A cop car’s siren has a frequency of 700. The speed of sound is 345 m/s. Sally moved her hand from the rest position back and forth along the floor 16 times in 4. cm/s. How high is the resulting wave? 21. what was the frequency of the vibrating object that produced the waves? c) What is the period of the vibrating object that produced the waves? d) What is the wavelength of the waves in the direction in which the vibrating object is moving? e) What is the frequency of these waves? f) At what speed is the vibrating object moving across the tank? 20. Hz. a vibrating object is producing circular waves in a tray of water as the object itself moves across the tray in a straight line from left to right at a constant speed.0 m/s. how fast is the other car traveling? 19. a) In what direction is the wavelength the same as it would be if the vibrating object always stayed in the same place? Use a ruler to determine what this wavelength is.15. Two identical cars are driving toward one another and sounding their horns. Sally and her lab partner held the ends of their spring 6. and the waves seem to be about 15 m apart.8 m/s (60 mph). Sketch the situation and determine the following: a) the wavelength of the wave Sally Sue sent b) the frequency of the wave produced c) the speed of the wave . Hz.00 meters apart. Since you know the building is 25. 16.00 s. If you are traveling at 26. B 6. True 2. 3. v0 = " v % $ ' f s = fo #v ! vo& " 343 % fo = 1350 Hz * $ ' = 1268Hz # 343 + 22. v f = 22. A&B 837 Hz 5. v ( f0 ! fs ) 343m / s * (470 ! 450)Hz = = 14.5 waves) 16 m/s . 357. 7. 0. vertically. right B 4.1 & v ( f0 ! fs ) 345m / s * (600 ! 512)Hz = = 59.5m / s 19. v f = gt 1 d= gt 2 so that 2 17. 0. 9.4 m / s 15.40 cm e. !=.2 m/s 13. 668 Hz c. a A left b. a. False 766 Hz " v % $ ' f s = fo #v ! vo& 10. 467Hz 413 Hz 273K + 35K v = 331m / s * = 352 m / s 273K " v % $ ' f s = fo #v ! vo& " 352 % fo = 1200 Hz * $ ' = 1354 Hz # 352 ! 40 & 16. v0 = v ( f0 ! fs ) 10 cm / s * (25 ! 20)Hz = = 2 cm / s f0 25Hz 21. 4 Hz 4m (4 nodes = 1. 0.6 m / s f0 470 Hz 440 Hz b.05s d. v0 = 11. 8.5cm f. v f = 2dg " v % $ ' f s = fo #v ! vo& 18.3m / s f0 600 Hz V = 59. 20 Hz c. 3m/s b. b.1.6m a. 22. 1167 Hz. 25 Hz 20. a.3m / s ! 26. 732 Hz. 12. 14.8m / s = 32. c.