A motor car blowing a horn of frequency 124 vib/ sec moves with a velocity 72 km/hr towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is 330 m /s)

Question

A motor car blowing a horn of frequency 124 vib/ sec moves with a velocity 72 km/hr towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is 330 m /s) (A) 109 vib/sec (B) 132 vib/sec (C) 140 vib/sec (D) 248 vib/sec

Tardigrade Admin · Accepted Answer

Similar to previous question <img class="img-fluid question-image" alt="image" src="https://cdn.tardigrade.in/img/question/physics/3dce847f88d2bb5744d454569cac3cb1-.png" /> The frequency of reflected sound heard by the driver n'=n((v-(-v0)/v-vs)) =n((v +v0/v-vs)) =124[(330+(72 × 5 / 18)/330-(72 × 5 / 18))] =140 vibration / sec

Q. A motor car blowing a horn of frequency $124 v ib / sec$ moves with a velocity $72 km / h r$ towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is $330 m / s$ )

109 vib/sec

132 vib/sec

140 vib/sec

248 vib/sec

Similar to previous question

The frequency of reflected sound heard by the driver
$n^{'} = n (\frac{v - ( - v _{0} )}{v - v _{s}})$
$= n (\frac{v + v _{0}}{v - v _{s}})$
$= 124 [\frac{330 + ( 72 \times 5/18 )}{330 - ( 72 \times 5/18 )}]$
$= 140$ vibration / $sec$

Q. A motor car blowing a horn of frequency 124vib/sec moves with a velocity 72km/hr towards a tall wall. The frequency of the reflected sound heard by the driver will be (velocity of sound in air is 330m/s)