$A$ source of frequency $150 \, Hz$ is moving in the direction of a person with a velocity of $110 \, m/s$. The frequency heard by the person will be .... $Hz$ (speed of sound in medium $= 330 \, m/s$)

$A$ sound source,emitting sound of constant frequency,moves with a constant speed and crosses a stationary observer. The frequency $(n)$ of sound heard by the observer is plotted against time $(t)$. Which of the following graphs represents the correct variation?

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 $kHz$)

An engine is moving on a circular track with a constant speed. It is blowing a whistle of frequency $500 \ Hz$. The frequency received by an observer standing stationary at the centre of the track is

$A$ police car moving at $22 \,ms^{-1}$ chases a motorcyclist. The policeman sounds a horn at $176 \,Hz$, while both of them move towards a stationary siren of frequency $165 \,Hz$. If the number of beats heard by the motorcyclist per second is zero, then the speed of the motorcycle is (Speed of sound in air $= 330 \,ms^{-1}$) (in $\,ms^{-1}$)

$A$ vehicle with a horn of frequency $n$ is moving with a velocity of $30\, m/s$ in a direction perpendicular to the straight line joining the observer and the vehicle. The observer perceives the sound to have a frequency $n + n_1$. Then (if the sound velocity in air is $300\, m/s$):