Two cars moving in opposite directions approach each other with speeds of $22 \, m s^{-1}$ and $16.5 \, m s^{-1}$ respectively. The driver of the first car blows a horn having a frequency of $400 \, Hz$. The frequency heard by the driver of the second car is ..... $Hz$ (velocity of sound is $340 \, m s^{-1}$)

$A$ source of sound $S$ in the form of a block kept on a smooth horizontal surface is connected to a spring, as shown in the figure. If the spring oscillates with an amplitude of $50 \,cm$ along the horizontal between the wall and the observer $O$, the maximum frequency heard by the observer is $12.5 \%$ more than the minimum frequency heard by him. If the mass of the source of sound is $100 \,g$, the force constant of the spring is (Speed of sound in air is $340 \,ms^{-1}$) (in $\,N m^{-1}$)

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 $330\,m/s$.

Two sources $A$ and $B$ are sounding notes of frequency $660 \, Hz$. $A$ listener moves from $A$ to $B$ with a constant velocity $u$. If the speed of sound is $330 \, m/s$,what must be the value of $u$ so that he hears $8$ beats per second?

$A$ police van,moving at $22 \, m/s$,chases a motorcyclist. The policeman sounds a horn at $176 \, Hz$,while both of them move towards a stationary siren of frequency $165 \, Hz$ as shown in the figure. If the motorcyclist does not observe any beats,his speed must be .... $m/s$ (take the speed of sound $= 330 \, m/s$).

Which of the following statements is false?