$A$ detector is released from rest over a source of sound of frequency $f_0 = 10^3 \, Hz$. The frequency observed by the detector at time $t$ is plotted in the graph. Given $g = 10 \, m/s^2$,find the speed of sound in air in $m/s$.

$A$ submarine $(A)$ travelling at $18\, km/hr$ is being chased along the line of its velocity by another submarine $(B)$ travelling at $27\, km/hr$. $B$ sends a sonar signal of $500\, Hz$ to detect $A$ and receives a reflected sound of frequency $v$. The value of $v$ is close to ... $Hz$ (Speed of sound in water $= 1500\, ms^{-1}$)

$A$ speeding motorcyclist sees a traffic jam ahead. He slows down to $36\, km\, h^{-1}$. He finds that the traffic has eased and a car moving ahead of him at $18\, km\, h^{-1}$ is honking at a frequency of $1392\, Hz$. If the speed of sound is $343\, m s^{-1}$,the frequency of the honk as heard by him will be .... $Hz$.

$A$ source of sound is moving towards a stationary observer with $\frac{1}{10}$ of the speed of sound. The ratio of apparent to real frequency is

$A$ source of sound of frequency $640 \,Hz$ is moving at a velocity of $\frac{100}{3} \,m/s$ along a road, and is at an instant $30 \,m$ away from a point $A$ on the road. $A$ person standing at $O$, $40 \,m$ away from the road, hears sound of apparent frequency $v^{\prime}$. The value of $v^{\prime}$ is (velocity of sound $= 340 \,m/s$): (in $\,Hz$)

$A$ whistle of frequency $540 Hz$ rotates in a horizontal circle of radius $2 m$ at an angular speed of $15 rad/s$. What is the highest frequency heard by a listener at rest with respect to the center of the circle (in $Hz$)? (Velocity of sound in air $= 330 m/s$)