18. Waves & Sound
The Doppler Effect
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- Multiple Choice
A police siren emits a sound somewhere around 700 Hz. If you are waiting at a red light, and a police car approaches you from behind and passes you, moving at a constant 30 m/s, what is the frequency you hear from the siren as it approaches you from behind? What about once it's passed you? Assume the air temperature to be 20°C.
3236views1comments - Multiple ChoiceA police radar gun used to measure the speed of cars emits an electromagnetic wave (a radio wave) with a frequency of In an area where the speed limit is what should be the shift in the frequency of the wave after reflecting off traffic that is exactly following the speed limit, driving toward the police officer?1464views
- Multiple ChoiceAs you stand beside the road singing a lovely note, your friend, Lisa, drives toward you at . What frequency does Lisa hear as she listens to you croon?745views
- Textbook Question
The shock-wave cone created by a space shuttle at one instant during its reentry into the atmosphere makes an angle of 58.0° with its direction of motion. The speed of sound at this altitude is 331 m/s. What is the Mach number of the shuttle at this instant?
1072views - Textbook Question
The siren of a fire engine that is driving northward at 30.0 m/s emits a sound of frequency 2000 Hz. A truck in front of this fire engine is moving northward at 20.0 m/s. What wavelength would this driver measure for these reflected sound waves?
1010views - Textbook Question
The siren of a fire engine that is driving northward at 30.0 m/s emits a sound of frequency 2000 Hz. A truck in front of this fire engine is moving northward at 20.0 m/s. (a) What is the frequency of the siren's sound that the fire engine's driver hears reflected from the back of the truck?
1814views - Textbook Question
A railroad train is traveling at 30.0 m/s in still air. The frequency of the note emitted by the train whistle is 352 Hz. What frequency is heard by a passenger on a train moving in the opposite direction to the first at 18.0 m/s and receding from the first?
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