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Standard VIII

Physics

Introduction to Sound Waves

A car has two...

Question

A car has two horns having a difference in frequency of 180 Hz. The car is approaching a stationary observer with a speed of 60 $m s^{- 1}$ . Calculate the difference in frequencies of the notes as heard by the observer, if velocity of sound in air is 330 $m s^{- 1}$ .

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Solution

Given : $Δ f = 180 H z$ $v_{s o u n d} = 330 m / s$ $v_{s} = 60 m / s$
Using Doppler effect :
$Δ f^{'} = Δ f [\frac{v_{s o u n d}}{v_{s o u n d} - v_{s}}]$
Or $Δ f^{'} = 180 [\frac{330}{330 - 60}] = 220 H z$

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A car has two horns having a difference in frequency of 180 Hz. The car is approaching a stationary observer with a speed of 60 ms−1. Calculate the difference in frequencies of the notes as heard by the observer, if velocity of sound in air is 330 ms−1.

Given : Δf=180 Hz vsound=330 m/s vs=60 m/sUsing Doppler effect :Δf′=Δf[vsoundvsound−vs]Or Δf′=180[330330−60]=220 Hz

A car has two horns having a difference in frequency of 180 Hz. The car is approaching a stationary observer with a speed of 60 $m s^{- 1}$ . Calculate the difference in frequencies of the notes as heard by the observer, if velocity of sound in air is 330 $m s^{- 1}$ .

Given : $Δ f = 180 H z$ $v_{s o u n d} = 330 m / s$ $v_{s} = 60 m / s$
Using Doppler effect :
$Δ f^{'} = Δ f [\frac{v_{s o u n d}}{v_{s o u n d} - v_{s}}]$
Or $Δ f^{'} = 180 [\frac{330}{330 - 60}] = 220 H z$