Posted by Melissa on Monday, June 4, 2012 at 1:12pm.
A car sounds its horn (502 Hz) as it approachs a pedestrian by the side of the road. The pedestrian has perfect pitch and determines that the sound from the horn has a frequency of 520 Hz. If the speed of sound that day was 340 m/s , how fast was the car travelling

physics  Elena, Monday, June 4, 2012 at 2:55pm
f(observed) = 520 Hz, f(source) = 502 Hz, u = 340 m/s
At source approaching
f(observed) = [v/(vu)] •f(source),
v =[f(obs)f(sour)] •u/ f(obs) =
= (520502) •340/520 = 18•340/520 =
=11.77 m/s.
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