$A$ source of sound of frequency $256 \ Hz$ is moving rapidly towards a wall with a velocity of $5 \ m/s$. The speed of sound is $330 \ m/s$. If the observer is between the wall and the source,then the number of beats per second heard will be .... $Hz$.

$A$ person carrying a whistle emitting a note of $272 \text{ Hz}$ is running towards a reflecting surface with a speed of $18 \text{ km/h}$. The speed of sound in air is $345 \text{ m/s}$. The number of beats heard by him is:

$A$ train moves towards a stationary observer with speed $34\, m/s$. The train sounds a whistle and its frequency registered by the observer is $f_1$. If the speed of the train is reduced to $17\, m/s$,the frequency registered is $f_2$. If the speed of sound is $340\, m/s$,then the ratio $f_1/f_2$ is

$A$ whistle sends out $256$ waves in a second. If the whistle approaches the observer with a velocity equal to $\frac{1}{3}$ of the velocity of sound in air,calculate the number of waves per second the observer will receive.

$A$ source emitting sound of frequency $288 \,Hz$ is tied to a string of $100 \,cm$ length and rotated with an angular velocity of $20 \,rad/s$ in the horizontal plane. The range of frequencies heard by an observer standing at a distance of $5 \,m$ from the source is (in $Hz$) (Speed of sound in air $= 340 \,m/s$)

$A$ motorcyclist is approaching a large wall with a velocity of $90\,km/hr$. $A$ car is chasing him with a velocity of $108\,km/hr$. If the car sounds a horn at $30\,Hz,$ the beat frequency heard by the motorcyclist is . . . . . . $Hz$. Take the velocity of sound $= 330\,m/s$.