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A motor car blowing a horn of frequency ...

A motor car blowing a horn of frequency `124vib//sec` moves with a velocity `72km//hr` towards a tall wall. The frequency of the reflectedf 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`

Text Solution

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The correct Answer is:
C

Similar to previous question
The frequency of reflected sound heard by the driver
`n'=n((v-(-v_0))/(v-v_S))=n((v+v_0)/(v-v_S))`
`=124[(330+(72xx5//18)/(330-(72xx5//18)]=140` vibration sec
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