Question

8. What is the frequency heard by a person driving at 18 m/s toward a blowing factory whistle (600 Hz) if

Answer 1

Answer:

631.7 Hz

Explanation:

The Doppler effect is a phenomenon that occurs when there is relative motion between an observer and a source of a wave. When this occurs, the is a change in the apparent frequency of the wave, as observed by the observer.

In particular, the new apparent frequency can be calculated as:

$f'=\frac{v\pm v_o}{v\pm v_s}f$

where

f is the real frequency

f' is the apparent frequency

v is the speed of the wave

$v_o$ is the velocity of the observer (positive if the observer is moving towards the source, negative if moving away)

$v_s$ is the velocity of the source (negative if the source is moving towards the observer, positive if moving away)

In this problem:

v = 340.6 m/s is the speed of the sound wave

f = 600 Hz is the real frequency of the sound

$v_o = +18 m/s$ is the velocity of the person

$v_s=0$ is the velocity of the source

Substituting, we find:

$f'=\frac{340.6+18}{340.6}(600)=631.7 Hz$