$A$ train blowing the whistle moves with a constant velocity $V$ away from an observer standing on the platform. The ratio of the natural frequency of the whistle $n$ to the apparent frequency is $1.2: 1$. If the train is at rest and the observer moves away from it at the same velocity $V$,the ratio of $n$ to the apparent frequency is (in $: 1$)

The velocity of sound is $340 \,m/s$. $A$ source of sound having a frequency of $90 \,Hz$ is moving towards a stationary observer with a speed of one-tenth that of sound. The apparent frequency of sound as heard by the observer is: (in $\,Hz$)

$A$ whistle of frequency $660 \,Hz$ moves in a circle of radius $1 \,m$ at an angular speed of $10 \,rad/s$. The highest frequency heard by a listener at a long distance and at rest with respect to the center of the circle is (Let speed of sound $= 340 \,m/s$.) (in $\,Hz$)

$A$ stationary source is emitting sound at a fixed frequency $f_0$,which is reflected by two cars approaching the source. The difference between the frequencies of sound reflected from the cars is $1.2 \%$ of $f_0$. What is the difference in the speeds of the cars (in $km/h$) to the nearest integer? The cars are moving at constant speeds much smaller than the speed of sound,which is $330 \ m/s$.

An observer is approaching with a speed $v$ towards a stationary source emitting sound waves of wavelength $\lambda_0$. The wavelength shift detected by the observer is (Take $c$ as the speed of sound).

The difference between the apparent frequency of a source of sound as perceived by an observer during its approach and recession is $2\%$ of the natural frequency of the source. If the velocity of sound in air is $300 \, m/s$,the velocity of the source is ... $m/s$ (Given that velocity of source < velocity of sound).