$A$ speeding motorcyclist sees a traffic jam ahead. He slows down to $36\, km\, h^{-1}$. He finds that the traffic has eased and a car moving ahead of him at $18\, km\, h^{-1}$ is honking at a frequency of $1392\, Hz$. If the speed of sound is $343\, m s^{-1}$,the frequency of the honk as heard by him will be .... $Hz$.

When an engine passes near a stationary observer,its apparent frequencies occur in the ratio $5/3$. If the velocity of sound is $340 \ m/s$,then the velocity of the engine is .... $m/s$.

$A$ bus is moving with a velocity of $5 \,m/s$ towards a wall. The driver blows the horn of frequency $165 \,Hz$. If the speed of sound in air is $335 \,m/s$, then after reflection of sound wave, the number of beats per second heard by the passengers in the bus will be

$A$ 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 $\,N m^{-1}$)

$A$ sound source is tied to one end of a string of length $50 \ cm$ and is rotated with an angular speed of $40 \ rad \ s^{-1}$ in a horizontal plane. The ratio of the maximum and minimum frequencies of the sound heard by an observer standing at a distance of $10 \ m$ from the fixed end of the string is (speed of sound in air $= 340 \ m \ s^{-1}$).

When the source of sound moves towards a stationary observer,the wavelength of sound received by him