Posted by Jane on Monday, February 22, 2010 at 3:25pm.
Speed of sound in air is about 344 m/s
Period of this wave is 1/f = 1/700 second
Wavelength = rate*time = 344/700 = .4914 meters
speed of ambulance relative to me if it is coming toward me = v
speed of wave relative to me = (344+v).
Time for it to get one wavelength closer =.4914/(344+v) = 1/756
so
344+v = 756*.4914 = 371.5
so
v = 27.52 m/s
27.52 m/s * 3600 s/h * 1 km/1000 m = 99 km/hr
im sure the answer ur getting is correct but ask yourself the units of the derived answer and compare it to the correct one..
using the doppler effect eq'n you can calculate the speed to be about 25 BUT ITS IN m/s which is EQUAL to 90km/h and its towards because the freqency increases
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