$A$ racing car moving towards a cliff sounds its horn. The driver observes that the sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If $v$ is the velocity of sound,the velocity of the car will be

An engine is moving on a circular track with a constant speed. It is blowing a whistle of frequency $500 \ Hz$. The frequency received by an observer standing stationary at the centre of the track is

An observer is standing $500 \,m$ away from a vertical hill. Starting between the observer and the hill, a police van sounding a siren of frequency $1000 \,Hz$ moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is $970 \,Hz$, the frequency of the sound heard after reflection from the hill (in $Hz$) is about, (velocity of sound $= 330 \,m/s$):

$A$ 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 = $330 \, m/s$)

An engine is moving with uniform speed along a circular track emitting a sound of frequency $400\, Hz$ as shown in the figure. The speed of the engine is $30\, m/s$ and the speed of sound is $330\, m/s$. An observer is standing inside the track. The maximum frequency observed by the observer is

$A$ 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 $\text{vibrations/sec}$?