173072 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{hr}$ sounds a whistle at frequency $640 \mathrm{~Hz}$ when it is $300 \mathrm{~m}$ away from the crossing. The speed of sound in air is 340 $\mathrm{m} / \mathrm{s}$. What will be the frequency heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?
173073
An observer is standing $500 \mathrm{~m}$ away from a vertical hill. Starting from a point between the observer and the hill, a police van moves towards the hill with uniform speed sounding a siren of frequency of $1000 \mathrm{~Hz}$. If the frequency of the sound heard by the observer directly from the siren is $970 \mathrm{~Hz}$, the frequency of the sound heard by the observer after reflection from the hill $(\mathrm{Hz})$ is nearly
(Velocity of sound in air $=300 \mathrm{~ms}^{-1}$ )
173074 Let $v_{s}$ be the speed of the source emitting waves, $n$ the actual frequency of the source of sound, $v$ the speed of the sound in the medium and $n$ ' the frequency of sound waves as perceived by a stationary of sound waves as perceived by a stationary observer to whom the source of sound is approaching. The formula for calculate for $n$ ' is
173072 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{hr}$ sounds a whistle at frequency $640 \mathrm{~Hz}$ when it is $300 \mathrm{~m}$ away from the crossing. The speed of sound in air is 340 $\mathrm{m} / \mathrm{s}$. What will be the frequency heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?
173073
An observer is standing $500 \mathrm{~m}$ away from a vertical hill. Starting from a point between the observer and the hill, a police van moves towards the hill with uniform speed sounding a siren of frequency of $1000 \mathrm{~Hz}$. If the frequency of the sound heard by the observer directly from the siren is $970 \mathrm{~Hz}$, the frequency of the sound heard by the observer after reflection from the hill $(\mathrm{Hz})$ is nearly
(Velocity of sound in air $=300 \mathrm{~ms}^{-1}$ )
173074 Let $v_{s}$ be the speed of the source emitting waves, $n$ the actual frequency of the source of sound, $v$ the speed of the sound in the medium and $n$ ' the frequency of sound waves as perceived by a stationary of sound waves as perceived by a stationary observer to whom the source of sound is approaching. The formula for calculate for $n$ ' is
173072 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{hr}$ sounds a whistle at frequency $640 \mathrm{~Hz}$ when it is $300 \mathrm{~m}$ away from the crossing. The speed of sound in air is 340 $\mathrm{m} / \mathrm{s}$. What will be the frequency heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?
173073
An observer is standing $500 \mathrm{~m}$ away from a vertical hill. Starting from a point between the observer and the hill, a police van moves towards the hill with uniform speed sounding a siren of frequency of $1000 \mathrm{~Hz}$. If the frequency of the sound heard by the observer directly from the siren is $970 \mathrm{~Hz}$, the frequency of the sound heard by the observer after reflection from the hill $(\mathrm{Hz})$ is nearly
(Velocity of sound in air $=300 \mathrm{~ms}^{-1}$ )
173074 Let $v_{s}$ be the speed of the source emitting waves, $n$ the actual frequency of the source of sound, $v$ the speed of the sound in the medium and $n$ ' the frequency of sound waves as perceived by a stationary of sound waves as perceived by a stationary observer to whom the source of sound is approaching. The formula for calculate for $n$ ' is
173072 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{hr}$ sounds a whistle at frequency $640 \mathrm{~Hz}$ when it is $300 \mathrm{~m}$ away from the crossing. The speed of sound in air is 340 $\mathrm{m} / \mathrm{s}$. What will be the frequency heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?
173073
An observer is standing $500 \mathrm{~m}$ away from a vertical hill. Starting from a point between the observer and the hill, a police van moves towards the hill with uniform speed sounding a siren of frequency of $1000 \mathrm{~Hz}$. If the frequency of the sound heard by the observer directly from the siren is $970 \mathrm{~Hz}$, the frequency of the sound heard by the observer after reflection from the hill $(\mathrm{Hz})$ is nearly
(Velocity of sound in air $=300 \mathrm{~ms}^{-1}$ )
173074 Let $v_{s}$ be the speed of the source emitting waves, $n$ the actual frequency of the source of sound, $v$ the speed of the sound in the medium and $n$ ' the frequency of sound waves as perceived by a stationary of sound waves as perceived by a stationary observer to whom the source of sound is approaching. The formula for calculate for $n$ ' is
173072 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{hr}$ sounds a whistle at frequency $640 \mathrm{~Hz}$ when it is $300 \mathrm{~m}$ away from the crossing. The speed of sound in air is 340 $\mathrm{m} / \mathrm{s}$. What will be the frequency heard by a person standing on a road perpendicular to the track through the crossing at a distance of 400 m from the crossing?
173073
An observer is standing $500 \mathrm{~m}$ away from a vertical hill. Starting from a point between the observer and the hill, a police van moves towards the hill with uniform speed sounding a siren of frequency of $1000 \mathrm{~Hz}$. If the frequency of the sound heard by the observer directly from the siren is $970 \mathrm{~Hz}$, the frequency of the sound heard by the observer after reflection from the hill $(\mathrm{Hz})$ is nearly
(Velocity of sound in air $=300 \mathrm{~ms}^{-1}$ )
173074 Let $v_{s}$ be the speed of the source emitting waves, $n$ the actual frequency of the source of sound, $v$ the speed of the sound in the medium and $n$ ' the frequency of sound waves as perceived by a stationary of sound waves as perceived by a stationary observer to whom the source of sound is approaching. The formula for calculate for $n$ ' is