get out your notes, pencil, and equation sheet. doppler effect and speed along a string
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Get out your notes, pencil, and equation sheet
Doppler Effect and Speed Doppler Effect and Speed Along a StringAlong a String
SoundSound
3D longitudinal wavesSound waves that can be heard
– Audible– 20-20,000 Hz.
Sound WavesSound Waves
Sound waves that are below 20Hz are called infrasonic – Ground Waves
Sound waves above 20,000 Hz are called ultrasonic – Dog whistles– Baby Pictures
Doppler Effect Doppler Effect Big Bang StyleBig Bang Style
https://www.youtube.com/watch?v=FQqCSpf2vLA
Doppler EffectDoppler Effect
As the object moves toward the observer, the speed of the waves are the speed of sound plus the speed of the object, therefore the waves are “crunched” together.– Pitch increases
Doppler EffectDoppler Effect
Doppler EffectDoppler Effect
Works for objects moving away from listener.
Doppler EffectDoppler Effect
Apparent Frequency– Away from observer
f’ = fo (Speed of sound/(speed of sound + vsource)) Negative velocity means the object is moving
towards the observer
Doppler EffectDoppler Effect
This also works when the observer is moving.
Doppler EffectDoppler Effect
Observer moving– f’ = fo ((speed of sound + v)/speed of sound)
V is negative when moving away from the object
Both observer and object moving– f’ = fo ((S+vobserver)/(S + vsource))
Question IQuestion I
On a standard day, the speed of sound is 345m/s. A whistle whose frequency is 1000Hz is moving toward an observer at a speed of 52.0m/s. What is the frequency of the sound heard by the observer?
AnswerAnswer
1180Hz
Question IIQuestion II
A train moving at a speed of 50m/s sounds its whistle, which has a frequency of 620Hz. The speed of sound on this particular day is 335m/s. Determine the frequency heard by the stationary observer A) as the train approaches and B) as the train moves away.
AnswerAnswer
730Hz and 540Hz
Question IIIQuestion III
On a standard day, the speed of sound is 345m/s. An observer is moving at a speed of 35m/s away from a whistle whose frequency is 1000Hz. What is the observed frequency of the whistle?
AnswerAnswer
898Hz
Works for LightWorks for Light
What about a duck????What about a duck????
Speed Along a StringSpeed Along a String
Speed Along a StringSpeed Along a String
Tension created by the hanging mass affects the speed of the wave.
The linear density of the string also affects the speed.– It is the mass of the string divided by the length
Speed Along a StringSpeed Along a String
Example IVExample IV
A uniform string has a mass of 0.40kg and a length of 5.0m. The tension in the string is provided by a 3.0kgmass. Find the speed of a pulse in this string.
AnswerAnswer
19m/s.
Sound IntensitySound Intensity
Intensity– Intensity = Power/Surface Area (W/m2)
Alexander Graham Bell– Logarithmic scale
decibels• dB
http://cnx.org/content/m42257/latest/?collection=col11406/latest
Example VExample V
A mass is used to provide tension in the string. The speed of the pulse traveling along the string is v. By what factor should the mass be multiplied in order for the pulse to have a speed of 3v?
AnswerAnswer
9 times greater mass
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