Question

The driver of a car approaching a vertical wall notices that the frequency of his car's horn changes from 440 hz to 480 hz when it gets reflected from the wall. If speed of sound in air is v then speed of car is

Answer 1

it should be the answer

Answer 2

Answer:

The speed of the car is 30 m/s.

Explanation:

Given that,

Apparent frequency =480 Hz

Frequency = 440 Hz

Let the speed of the car be v.

We know that,

The speed of sound in air is 330 m/s.

This is the case when the source of sound is stationary and the observer is moving .

We need to calculate the speed of the car

Using formula of the apparent frequency heard by observer

$f'=\dfrac{v_{s}+v_{o}}{}\times f$

Put the value into the formula

$480=\dfrac{330+v}{330}\times440$

$v=\dfrac{480\times330}{440}-330$

$v=30\ m/s$

Hence, The speed of the car is 30 m/s.