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

$A$ highway truck has two horns $A$ and $B$. When sounded together, the driver records $50$ beats in $10$ seconds. With horn $B$ blowing and the truck moving towards a wall at a speed of $10 \,m/s$, the driver notices a beat frequency of $5 \,Hz$ with the echo. When the frequency of $A$ is decreased, the beat frequency with the two horns sounded together increases. Calculate the frequency of horn $A$. (Speed of sound in air $= 330 \,m/s$) (in $\,Hz$)

Two trains,one coming towards and another going away from an observer,both at $4 \; m/s$,produce a whistle simultaneously of frequency $300 \; Hz$. Find the number of beats produced. (Assume the speed of sound $v = 332 \; m/s$)

When a source of sound crosses a stationary observer,the change in apparent frequency of sound observed by the observer,when $V_s << V$,will be -

$A$ source with a frequency of $500 \,Hz$ moves towards a stationary observer with a velocity of $30 \,m/s$. What frequency (in $Hz$) will the observer hear? (The speed of sound in air is $330 \,m/s$.)

When the observer 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 $F_1 / F_2 = 2$,then $V / V_1$ is equal to: