$A$ source and an observer approach each other with the same velocity $50 \, m/s$. If the apparent frequency is $435 \, s^{-1}$,then the real frequency is .... $s^{-1}$ (Take speed of sound $v = 332 \, m/s$)

At what speed should a source of sound move so that the observer finds the apparent frequency equal to half the original frequency?

$A$ 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 $330 \ m/s$.

$A$ source and an observer move away from each other with a velocity of $10\; m/s$ with respect to the ground. If the observer finds the frequency of sound coming from the source as $1950\; Hz$,then the actual frequency of the source is .... $Hz$ (velocity of sound in air = $340\; m/s$).

The driver of a car travelling with a speed $V_1 \ m/s$ towards a wall sounds a siren of frequency $n \ Hz$. If the velocity of sound in air is $V \ m/s$,then the frequency of the sound reflected from the wall and as heard by the driver in $Hz$ is

$A$ whistle giving out $450 Hz$ approaches a stationary observer at a speed of $33 m/s$. The frequency heard by the observer in $Hz$ is (Take speed of sound $v = 330 m/s$)