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 0.844 times smaller than that 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

Answer:

Explanation:

Given

Apparent Frequency $f'=0.844 f_0$

speed of sound $v=343 m/s$

Applying Doppler Effect Formula

$f'=f_0(\frac{v+v_0}{v-v_s})$

where $v_0=$speed of observer

$v_s=$speed of source

here $v_o=0$ as he is listening and at rest

$0.844f_0=f_0(\frac{343+0}{343-v_s})$

$343-v_s=406.39$

$v_s=-63.39 m/s$

i.e. car is moving away from observer with 63.99 m/s