$A$ 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 $: 1$)

$A$ car moving towards a wall at a velocity of $30 \, m/s$ sounds a horn of frequency $600 \, Hz$. What frequency $(Hz)$ will the driver hear? (Speed of sound in air = $330 \, m/s$)

$A$ small source of sound vibrating at a frequency $500 Hz$ is rotated along a circle of radius $\frac{100}{\pi} cm$ at a constant angular speed of $5$ revolutions per second. The minimum and maximum frequency of the sound observed by a listener situated in the plane of the circle is (Speed of sound is $332 ms^{-1}$)

$A$ 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 moves towards a stationary source of sound,with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency (in $\%$)?

$A$ stationary observer receives sound from two identical tuning forks, one of which approaches and the other one recedes with the same speed $v$ (much less than the speed of sound). The observer hears $2 \; \text{beats/sec}$. The oscillation frequency of each tuning fork is $\nu_{0} = 1400 \; \text{Hz}$ and the velocity of sound in air is $c = 350 \; \text{m/s}$. The speed of each tuning fork is close to: