An engine moving towards a wall with a velocity $50 \ m/s$ emits a note of $1.2 \ kHz$. The speed of sound in air is $350 \ m/s$. The frequency of the note after reflection from the wall as heard by the driver of the engine is: (in $kHz$)

The frequency of the echo will be $.......Hz$ if a car blowing a whistle of frequency $320\,Hz$ is moving with a velocity of $36\,km/h$ towards a hill from which an echo is heard by the car driver. The velocity of sound in air is $330\,m/s$.

$A$ source and a listener are both moving towards each other with a speed of $\frac{V}{10}$ (where $V$ is the speed of sound). If the frequency of the sound note emitted by the source is $n$,then the frequency heard by the listener would be nearly:

$A$ car travelling at a speed of $54 \ km/h$ towards a wall sounds a horn of frequency $400 \ Hz$. The difference in the frequencies of two sounds, one received directly from the car and the other reflected from the wall, noticed by a person standing between the car and the wall is (speed of sound in air is $335 \ m/s$):

$A$ car sounding a horn of frequency $1000 \text{ Hz}$ passes an observer. The ratio of frequencies noted by the observer before and after the car passes is $11:9$. If the speed of sound is $V$,what is the speed of the car?

$A$ musician using an open flute of length $50\,cm$ produces second harmonic sound waves. $A$ person runs towards the musician from another end of a hall at a speed of $10\,km/h.$ If the wave speed is $330\,m/s,$ the frequency heard by the running person shall be close to...... $Hz$