$A$ policeman blows a whistle of frequency $400 \ Hz$. $A$ car driver is approaching the policeman. The speed of the car is $54 \ km/h$. The change in frequency experienced by the driver,when the driver approaches the policeman and after he crosses the policeman,is ... $Hz$ [Velocity of sound is $350 \ m/s$]

When the source of sound and the observer both are moving towards each other,the observer will hear:

$A$ bus is moving with a velocity of $5 \, ms^{-1}$ towards a huge wall. The driver sounds a horn of frequency $165 \, Hz$. If the speed of sound in air is $335 \, ms^{-1}$, the number of beats heard per second by the passengers in the bus will be:

$A$ source with a frequency of $90 \, \text{vibrations/sec}$ moves towards a stationary observer with a velocity of $1/10 \, V$, where $V$ is the speed of sound. What frequency will the observer hear in $\text{vibrations/sec}$?

The engine of a train moving with speed $10\,ms^{-1}$ towards a platform sounds a whistle at frequency $400\,Hz$. The frequency heard by a passenger inside the train is $........\,Hz$ (neglect air speed. Speed of sound in air $330\,ms^{-1}$). (in $,Hz$)

$A$ 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: