B M Sharma Solutions for Chapter: Sound Wave And Doppler Effect, Exercise 1: DPP

A person feels $2.5\%$ difference of frequency of a motor-car horn. If the motor-car is moving to the person and the velocity of sound is ${\text{320 m s}}^{-1}$, then the velocity of car will be _____ $\mathrm{m} {\mathrm{s}}^{-1}$.

A source of sound emitting a note of frequency $200 \mathrm{Hz}$ moves towards an observer with a velocity $v$ equal to the velocity of sound. If the observer also moves away from the source with the same velocity $v$, the apparent frequency heard by the observer is _____$\mathrm{Hz}$.

A source of sound is travelling towards a stationary observer. The frequency of the sound heard by the observer is of three times the original frequency. The velocity of sound is $v \mathrm{m} {\mathrm{s}}^{-1}$. If the speed of the source is $\frac{xv}{3}$ then $x=$ _____.

A source and listener are both moving towards each other with speed $\frac{V}{10}$, where $V$ is the speed of sound. If the frequency of the note emitted by the source is $f$, the frequency heard by the listener would be nearly _____$f$. (Give solution in decimal with two decimal place accuracy).

Two trains are moving towards each other at speeds of $20 \mathrm{m} {\mathrm{s}}^{-1}$ and $15 \mathrm{m} {\mathrm{s}}^{-1}$ relative to the ground. The first train sounds a whistle of frequency $600 \mathrm{Hz}$. The frequency of the whistle heard by a passenger in the second train before the train meets is _____ $\mathrm{Hz}$  (The speed of sound in air is $340 \mathrm{m} {\mathrm{s}}^{-1}$.)

 A car sounding a horn of frequency $1000 \mathrm{Hz}$ passes an observer. The ratio of frequencies of the horn noted by, the observer before and after passing of the car is $11:9$. If the speed of sound is $V$, If the speed of the car is $\frac{V}{x}$ then $x=$_____.

A boy is walking away from a wall towards an observer at a speed of $1 \mathrm{m} {\mathrm{s}}^{-1}$ and blows a whistle whose frequency is $680 \mathrm{Hz}$. The observer will hear _____ beats per second. (Velocity of sound in air $=340 \mathrm{m} {\mathrm{s}}^{-1}$) 

When an engine passes near to a stationary observer, then its apparent frequencies occur in the ratio $\frac{5}{3}$. If the velocity of the engine is _____ $\mathrm{m} {\mathrm{s}}^{-1}$.