Question

From a vantage point very close to the track at a stock car race, you hear the sound emitted by a moving car. You detect a frequency that is 0.835 times as small as the frequency emitted by the car when it is stationary. The speed of sound is 343 m/s. What is the speed of the car?

Answer 1

The speed of the car is 67.77 m/s and it is moving away from the observer.

Step-by-step explanation:

The apparent frequency is given as

`f' = f( [v - vo])/( [v - vs])`

Here

o is the observer

s is the source which is car

v is the speed of sound = 343 m/s

f = true frequency emitted by the car (when stationary)

f ' = 0.835 f

so

`f' = f( [v - vo])/( [v - vs])\\0.835 f= f( [v - vo])/( [v - vs])\\0.835 = ( [343 - 0])/( [343 - vs])\\0.835=(343)/(343-x)\\x=-67.77 m/s`

The speed of the car is 67.77 m/s and it is moving away from the observer.