An observer moves towards a stationary source of sound of frequency $n$. The apparent frequency heard by him is $2n$. If the velocity of sound in air is $332 \, m/s$,then the velocity of the observer is .... $m/s$.

An observer moves towards a stationary source of sound with a speed $\frac{1}{5}$th that of sound. The frequency of the sound emitted by the source is $f$. The apparent frequency recorded by the observer is

Consider two tuning forks with natural frequency $250 \,Hz$. One is moving away and another is moving towards a stationary observer at the same speed. If the observer hears beats of frequency $5 \,Hz$, then the speed of the tuning fork is: (Given, speed of sound wave is $350 \,m/s$.) (in $\,m/s$)

$A$ whistle producing sound waves of frequencies $9500 \ Hz$ and above is approaching a stationary person with speed $v \ ms^{-1}$. The velocity of sound in air is $300 \ ms^{-1}$. If the person can hear frequencies up to a maximum of $10,000 \ Hz$,the maximum value of $v$ up to which he can hear the whistle is ... $ms^{-1}$.

$A$ car sounding a horn of frequency $1000 \ Hz$ passes a stationary observer. The ratio of frequencies of the horn noted by the observer before and after passing the car is $11:9$. If the speed of sound is $v$,the speed of the car is:

$A$ police car moving at $22 \,ms^{-1}$ chases a motorcyclist. The policeman sounds a horn at $176 \,Hz$, while both of them move towards a stationary siren of frequency $165 \,Hz$. If the number of beats heard by the motorcyclist per second is zero, then the speed of the motorcycle is (Speed of sound in air $= 330 \,ms^{-1}$) (in $\,ms^{-1}$)