What frequency is heard by an observer who hears the 450 Hz siren on a police car
traveling at 35 m/s away from her? Assume that the velocity of sound in air is 345 m/s.
Is this the correct?
450*345/(345+35)
=408Hz
yes, just did this a minute ago
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/dopp.html#c4
To calculate the frequency heard by an observer, you need to take into account the Doppler effect. The Doppler effect is the change in frequency or pitch that occurs when there is relative motion between the source of the sound and the observer.
The formula to calculate the observed frequency (f') is given by:
f' = (v + vo) / (v + vs) * f
Where:
f' is the observed frequency,
f is the emitted frequency by the source,
v is the velocity of sound in air,
vo is the velocity of the observer relative to the medium,
and vs is the velocity of the source relative to the medium.
In this case, the emitted frequency is 450 Hz, the velocity of sound in air is 345 m/s, and the velocity of the police car is 35 m/s away from the observer. The observer is stationary, so her velocity (vo) is 0.
By substituting the values into the formula, we can calculate the observed frequency:
f' = (345 + 0) / (345 + (-35)) * 450
f' = 345 / 310 * 450
f' = 1.1129032258064516 * 450
f' ≈ 500.806 Hz (rounded to three decimal places)
Therefore, the correct observed frequency heard by the observer is approximately 500.806 Hz, not 408 Hz as initially calculated.