The frequency will sound different if we hear a sound source
moving relative to us. This phenomenon is called the Doppler Effect
in Physics. An ambulance sounds a siren at 1515 Hz and passes a
cyclist moving at 2.12 m / s. After the ambulance passed, the
cyclist heard a siren sound at a frequency of 1501 Hz. The speed of
sound in the air is about 343 m / s.
What is the speed (speed) of the ambulance in (m / s)?
Let us say that the speed of the ambulance is v. It is given that the speed of the cyclist is 2.12 m/s. Since the ambulances passes by the cyclist we can assume that the speed of the ambulance is greater than the cyclist. Hence the heard frequency equation will be,
Here vs is the speed of source, in our case it will be relative speed between the cyclist and the ambulance which is,
Substituting the heard and source frequencies into the equation we can calculate the speed of ambulance as,
Hence the speed of the ambulance is 5.32 m/s.
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