When the listener moves towards a stationary source with velocity $V_1$,the apparent frequency of the emitted note is $F_1$. When the observer moves away from the source with velocity $V_1$,the apparent frequency is $F_2$. If $V$ is the velocity of sound in air and $\frac{F_1}{F_2} = 2$,then find the ratio $\frac{V}{V_1}$.

$A$ and $B$ are two sources generating sound waves. $A$ listener is situated at $C$. The frequency of the source at $A$ is $500 \, Hz$. $A$ now moves towards $C$ with a speed of $4 \, m/s$. The number of beats heard at $C$ is $6$. When $A$ moves away from $C$ with a speed of $4 \, m/s$,the number of beats heard at $C$ is $18$. The speed of sound is $340 \, m/s$. The frequency of the source at $B$ is ..... $Hz$.

$A$ toy-car,blowing its horn,is moving with a steady speed of $5\, m/s$,away from a wall. An observer,towards whom the toy car is moving,is able to hear $5\, beats$ per second. If the velocity of sound in air is $340\, m/s$,the frequency of the horn of the toy car is close to ... $Hz$

$A$ bat flies at a steady speed of $4 \,ms^{-1}$ emitting a sound of $f = 90 \times 10^{3} \,Hz$. It is flying horizontally towards a vertical wall. The frequency of the reflected sound as detected by the bat will be (take velocity of sound in air is $330 \,ms^{-1}$)

$A$ source of sound is travelling with a velocity of $40 \, km/h$ towards an observer and emits sound of frequency $2000 \, Hz$. If the velocity of sound is $1220 \, km/h$,what is the apparent frequency heard by the observer in $Hz$?

Two sources $A$ and $B$ are sending notes of frequency $680 \ Hz$. $A$ listener moves from $A$ towards $B$ with a constant velocity $u$. If the speed of sound in air is $340 \ ms^{-1}$, what must be the value of $u$ so that he hears $10$ beats per second (in $ms^{-1}$)?