$A$ 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:

Two trucks heading in opposite directions, each with a speed of $0.1 u$, approach each other. The speed of sound is $u$. The driver of the first truck sounds his horn with a frequency of $495 \,Hz$. Let $v_1$ and $v_2$ be the frequencies heard by the driver of the second truck when the trucks are approaching each other and when the trucks have passed each other, respectively. The magnitude of $v_1 - v_2$ is (in $\,Hz$)

$A$ car $P$ travelling at $20\,ms^{-1}$ sounds its horn at a frequency of $400\,Hz$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40\,ms^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately $.......\,Hz$. [Take,velocity of sound $= 360\,ms^{-1}$]

Match Column-$A$ with Column-$B$.

Column-$A$	Column-$B$
$(a)$ When source of sound and listener move towards wall.	$(i)$ Listener would hear a sound with same frequency as that of source.
$(b)$ When source of sound and listener move away from each other.	$(ii)$ Listener would hear a sound with frequency smaller than that of source.
	$(iii)$ Frequency of echo would be greater than that of source.

$A$ police car moving at $22 \ m/s$ chases a motorcyclist. The policeman sounds his horn at $176 \ Hz$,while both of them move towards a stationary siren of frequency $165 \ Hz$. Calculate the speed of the motorcycle,if it is given that he does not observe any beats. (in $m/s$)

Two passenger trains moving with a speed of $108\, km/h$ cross each other. One of them blows a whistle whose frequency is $750\, Hz$. If the speed of sound is $330\, m/s$,then the passengers sitting in the other train,after the trains cross each other,will hear a sound whose frequency is .... $Hz$.