A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed \nu ms-1 The velocity of sound in air is 300 ms-1. If the person can hear frequencies upto a maximum of 10000 Hz , the maximum value of \nu upto which he can hear the whistle is

  • Option 1)

    30ms^{-1}

  • Option 2)

    15\sqrt{2}ms^{-1}

  • Option 3)

    15/\sqrt{2}ms^{-1}

  • Option 4)

    15 ms^{-1}

 

Answers (1)

As we learnt in

Frequency of sound when observer is stationary and source is moving towards observer -

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

- wherein

C= speed of sound

V_{\Delta }= speed of source

\nu _{0}= original frequency

\nu {}'= apparent frequency

 

 

 

\frac{\upsilon '}{\upsilon }=\frac{v_{s}}{v_{s}-v}

Where v_{s} is the velocity of sound in air.

\frac{10000}{9500}=\frac{300}{300-v}

\Rightarrow (300-v)=285\Rightarrow v=15\; m/s

Correct option is 4.


Option 1)

30ms^{-1}

This is an incorrect option.

Option 2)

15\sqrt{2}ms^{-1}

This is an incorrect option.

Option 3)

15/\sqrt{2}ms^{-1}

This is an incorrect option.

Option 4)

15 ms^{-1}

This is the correct option.

Preparation Products

Knockout JEE Main April 2021 (One Month)

Personalized AI Tutor and Adaptive Time Table, Self Study Material, Weekend Live Classes, Mentorship from our Experts, Unlimited Mock Tests and Personalized Analysis Reports, 24x7 Doubt Chat Support,.

₹ 14000/- ₹ 4999/-
Buy Now
Knockout JEE Main May 2021

Personalized AI Tutor and Adaptive Time Table, Self Study Material, Weekend Live Classes, Mentorship from our Experts, Unlimited Mock Tests and Personalized Analysis Reports, 24x7 Doubt Chat Support,.

₹ 22999/- ₹ 9999/-
Buy Now
Test Series JEE Main May 2021

Unlimited Chapter Wise Tests, Unlimited Subject Wise Tests, Unlimited Full Mock Tests, Get Personalized Performance Analysis Report,.

₹ 6999/- ₹ 2999/-
Buy Now
Knockout JEE Main May 2022

Personalized AI Tutor and Adaptive Time Table, Self Study Material, Weekend Live Classes, Mentorship from our Experts, Unlimited Mock Tests and Personalized Analysis Reports, 24x7 Doubt Chat Support,.

₹ 34999/- ₹ 14999/-
Buy Now
JEE Main Rank Booster 2021

Booster and Kadha Video Lectures, Unlimited Full Mock Test, Adaptive Time Table, 24x7 Doubt Chat Support,.

₹ 13999/- ₹ 6999/-
Buy Now
Boost your Preparation for JEE Main 2021 with Personlized Coaching
 
Exams
Articles
Questions