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
http://hyperphysics.phy-astr.gsu.edu/hbase/sound/dopp.html#c4
Yes, your calculation is correct. The frequency heard by an observer is given by the formula:
f' = (f * v) / (v + vo)
Where:
f' is the frequency heard by the observer
f is the actual frequency emitted by the source
v is the velocity of sound in air
vo is the velocity of the source relative to the medium
Plugging in the values:
f = 450 Hz
v = 345 m/s
vo = 35 m/s
f' = (450 * 345) / (345 + 35)
= 155,250 / 380
≈ 408 Hz
So, the frequency heard by the observer is approximately 408 Hz.
Yes, you are correct. To calculate the frequency heard by an observer when a source of sound is moving away from them, you can use the formula:
Observed frequency = (Source frequency * Speed of sound) / (Speed of sound + Observer's speed towards or away from the source).
In this case, the source frequency is 450 Hz and the speed of sound in air is 345 m/s. The observer is stationary, so their speed is 0. The police car, however, is traveling away from the observer at a speed of 35 m/s.
Using the formula, we can substitute the values:
Observed frequency = (450 Hz * 345 m/s) / (345 m/s + 35 m/s)
Simplifying this expression gives:
Observed frequency = 155250 Hz / 380 m/s
The calculated observed frequency is approximately 408 Hz.