The frequency of a car horn changes from $400\, Hz$ to $500\, Hz$ as the car approaches a vertical wall. If the speed of sound is $330\, m/s$,then the speed of the car is $.....\, km/h$.

When an engine passes near a stationary observer,its apparent frequencies occur in the ratio $5/3$. If the velocity of sound is $340 \ m/s$,then the velocity of the engine is .... $m/s$.

$A$ whistle emitting a loud sound of frequency $540 \,Hz$ is whirled in a horizontal circle of radius $2 \,m$ at a constant angular speed of $15 \,rad/s$. The speed of sound is $330 \,m/s$. The ratio of the highest to the lowest frequency heard by a listener standing at rest at a large distance from the centre of the circle is

When a train is approaching a stationary observer,the apparent frequency of the whistle of the train is $n_1$,and when the train is moving away from the observer,the apparent frequency is $n_2$. The frequency of the whistle noticed by the observer when he moves with the train is . . . . . . .

Two cars are moving towards each other at the speed of $50 \,m/s$. If one of the cars blows a horn at a frequency of $250 \,Hz$, the wavelength of the sound perceived by the driver of the other car is (Speed of sound in air $= 350 \,m/s$) (in $\,cm$)

$A$ car moving towards a cliff emits sound of frequency '$n$'. If the difference in frequencies of the horn and its echo heard by the driver of the car is $10 \%$ of '$n$',then the speed of the car is nearly (Speed of sound in air is $336 \ m/s$) (in $m/s$)