$A$ musician on a moving vehicle plays a tone at $880 \ Hz$. When the vehicle is approaching a listener,the listener receives it as an $888 \ Hz$ tone. What is the speed of the vehicle (in $m \ s^{-1}$)? (Assume the velocity of sound is $333 \ m \ s^{-1}$)

If a source emitting waves of frequency $F$ moves towards an observer with a velocity $V/3$ and the observer moves away from the source with a velocity $V/4$,the apparent frequency as heard by the observer will be ($V=$ velocity of sound).

An observer moves towards a stationary source of sound of frequency $n$. The apparent frequency heard by him is $2n$. If the velocity of sound in air is $332 \, m/s$,then the velocity of the observer is .... $m/s$.

Two cars $A$ and $B$ are moving away from each other in opposite directions. Both cars are moving with a speed of $20 \, ms^{-1}$ with respect to the ground. If an observer in car $A$ detects a frequency of $2000 \, Hz$ from the sound source in car $B$,what is the natural frequency of the sound source of car $B$ (in $Hz$)? (Speed of sound in air $= 340 \, ms^{-1}$)

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 $340 \, m s^{-1}$)

$A$ man standing on a platform observes that the frequency of the sound of a whistle emitted by a train drops by $140 \, Hz$. If the velocity of sound in air is $330 \, m/s$ and the speed of the train is $70 \, m/s$,the frequency of the whistle is .......... $Hz$.