Final answer:
The ambulance's speed can be calculated using the Doppler effect equations and the observed 7.23% decrease in frequency. Assuming a sound speed of 343 m/s, the ambulance is moving at approximately 34.3 m/s or about 77 mph.
Step-by-step explanation:
The phenomenon you're asking about is known as the Doppler effect, which occurs when a source of sound moves relative to an observer. To determine the speed of the ambulance based on a 7.23% decrease in frequency perceived by the observer, we can use the Doppler effect equations:
f' = f * ((v + vo) / (v + vs)) when the source is moving towards the observer, and f' = f * ((v - vo) / (v - vs)) when the source is moving away, where f' is the observed frequency, f is the emitted frequency, v is the speed of sound, vo is the speed of the observer (which is zero in this case as the observer is stationary), and vs is the speed of the source (ambulance). Given the percentage change, we can express this as f' = f * (1 - 0.0723) when the ambulance moves away.
To solve for vs, the speed of the ambulance, we'll set up the equation based on the percent change provided:
f * ((v - 0) / (v - vs)) = f * (1 - 0.0723)
Assuming the speed of sound in air v is 343 m/s (a common approximation), we solve for vs and find that the ambulance's speed is approximately 34.3 m/s, which converts to roughly 77 mph.