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Shahzad7317
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Homework Statement
A listener L hears the siren from a moving police car ,S, which is moving away from the listener with a speed of v = 20.0 m/s. The listener is moving at 10.0 m/s towards the car. There is a wind blowing with a speed of v(wind)= 10.0 m/s from S to L. The siren is emitting sound at a frequency (f) of 800 Hz. The velocity of sound in air is 343 m/s. Calculate the frequency (f') heard by the listener and the wavelength (λ) of that wave.
Homework Equations
f' = f(v +/- vD) / (v -/+ vS)
v = fλ
The Attempt at a Solution
Finding the new frequency is easy:
f' = (800hz)(343+10+ 10)/(343+10+20)
f' = 779 Hz. But now for finding the wavelength I'm confused.
I know it's λ = v/f'
but is it:
v = 343m/s (the speed of sound in still air)
v= 343+10 m/s (the speed of sound + the speed of the wind)
v= 343+10+20 m/s (the speed of sound + the speed of the wind + the speed of the source)
or something else?
Any help would be much appreciated.
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