$A$ train is approaching a platform with a speed of $10 \,ms^{-1}$ while blowing a whistle of frequency $340 \,Hz$. What is the frequency of the whistle heard by a stationary observer on the platform (in $\,Hz$)? (Given speed of sound $= 340 \,ms^{-1}$)

The Doppler effect is applicable for

An engine giving a whistle is moving towards a stationary observer with a speed of $110\, m/s$. What will be the ratio of the frequency of the whistle heard when the engine is approaching and receding from the observer? (Speed of sound $= 330\, m/s$)

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 $330\,m/s$.

$A$ whistle producing sound waves of frequencies $9500 \ Hz$ and above is approaching a stationary person with speed $v \ ms^{-1}$. The velocity of sound in air is $300 \ ms^{-1}$. If the person can hear frequencies up to a maximum of $10,000 \ Hz$,the maximum value of $v$ up to which he can hear the whistle is ... $ms^{-1}$.

$A$ train whistling at a constant frequency is moving towards a station at a constant speed $V_S$. The train goes past a stationary observer on the station. The frequency $n'$ of the sound as heard by the observer is plotted as a function of time $t$. Identify the expected curve.