Q&A - Ask Doubts and Get Answers
Q

Help me answer: A motor car blowing a horn of frequency 120 vib/s moves with velocity 90km/hr. The frequency of the sound heard (Reflected) by the driver will be (speed of sound in air is 325 m/s)

A motor car blowing a horn of frequency 120 vib/s moves with velocity 90km/hr. The frequency of the sound heard (Reflected) by the driver will be (speed of sound in air is 325 m/s)

  • Option 1)

    109 vib/s

  • Option 2)

    132 vib/s

  • Option 3)

    140 vib/s

  • Option 4)

    248 vib/s

 
Answers (1)
102 Views

n'=\left [ \frac{v+v_{0}}{v-v_{s}} \right ]n

n'=120\left [ \frac{325+90\times 518}{325-90\times 518} \right ]= 140

 

frequency of sound when source is moving towards the observer and observer is moving away from source -

\nu {}'= \nu _{0}.\frac{C-V_{0}}{C-V_{s}}

- wherein

C= Speed of sound

V_{0}= Speed of observer

V_{s}= speed of source

\nu _{0 }= Original frequency

\nu {}'= apparent frequency

 

 


Option 1)

109 vib/s

This is incorrect

Option 2)

132 vib/s

This is incorrect

Option 3)

140 vib/s

This is correct

Option 4)

248 vib/s

This is incorrect

Exams
Articles
Questions