Physics 3: Springs & Waves Flashcards Preview

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Flashcards in Physics 3: Springs & Waves Deck (36)
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31

Doppler Effect

difference between the perceived frequency of a sound and its actual frequency when the source of the sound and the sound's detector are moving relative to each other

  • If the source and detector are moving toward each other, the perceived frequency f′ is greater than the actual frequency f,
  • if the source and detector are moving away from each other, the perceived frequency f′ is less than the actual frequency f. 
  • f'=f[(v +/-vD)/ (v-/+ vs)
  • where v is the speed of sound in the medium, vD is the speed of the detector relative to the medium, and vS is the speed of the source relative to the medium. The upper sign on vD and vS is used when the detector and the source are getting closer together. The lower sign is used when the detector and the source are going farther away from each other.

32

strings (standing waves)

λ=(2L)/n

where n is a positive nonzero integer (n = 1, 2, 3,… )

Pattern:  etc.

 

From relationship that f=v/λ, the possible frequencies are:

f=(nv)/2L

where n is a positive nonzero integer (n = 1, 2, 3,… ).

33

open pipes

λ=(2L)/n

where n is a positive nonzero integer (n = 1, 2, 3,… )

Pattern:  etc.

 

From relationship that f=v/λ, the possible frequencies are:

f=(nv)/2L

where n is a positive nonzero integer (n = 1, 2, 3,… ).

34

 harmonic series

fundamental frequency( first harmonic): lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string

second harmonic: frequency of the standing wave given by n = 2 is known as the firstovertone or  This standing wave has one-half the wavelength and twice the frequency of the first harmonic. All the possible frequencies that the string can support form its harmonic series. 

 

The waveforms of the first three harmonics for a string of length L are shown.(Note: N stands for node and A stands for antinode.)

35

Closed Pipes

λ=4L/n

where n is odd integers only (n = 1, 3, 5,… ). The frequency of the standing wave in a closed pipe is f=nv/4L

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