Question

An opera singer in a convertible sings a note at 600 Hz while cruising down the highway at 90km/hr. What is the frequency heard by a person standing beside the road in front of the car?

Answer 1

Answer:

$f=647.17Hz$

Explanation:

Given data

Frequency fs=600 Hz

Velocity Vs=90 km/hr =25 m/s

Speed of sound v=343 m/s

To find

Frequency f heard by a person standing beside the road in front of the car

Solution

From Doppler's effect we know that:

$f=f_{s}(\frac{v+vL}{v+vs} )\\ as\\vL=0$

Here Vs is negative as the source is moving towards listener

$f=fs(\frac{v+0}{v-vs} )\\f=(600Hz)(\frac{343m/s+0}{343m/s-25m/s} )\\f=647.17Hz$