1) We are in an automobile traveling at 43.2 mph down a street. We approach a ta

Question

1) We are in an automobile traveling at 43.2 mph down a street. We approach a tall brick wall and honk our horn which has a pitch of 245.0 Hz.

(a) Find the frequency of the sound we can hear reflected off the wall and coming back to us. Hint: The wall "observes" a Doppler-shifted frequency, and then sends that frequency back to you. Since you are moving relative to the wall, you will hear the frequency that the wall sends back to you Doppler shifted again. Use 343 m/s for the speed of sound.

(b) We can hear beats from interference between the reflected sound and the sound directly from the horn. Find the beat frequency. The speed of sound is 343 m/s.

(Answer: _____Hz (

Explanation / Answer

1) (a)
V= 43.2 mph = 19.31213 m/s
f (v+vauto / v-vauto) = 245.0Hz ((343 + 19.31213)/(343 - 19.31213)) = 274.23478 Hz

(b)

2)

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