173094 A train approaching a railway crossing at a speed of $180 \mathrm{kmh}^{-1}$ sounds a short whistle at a frequency $600 \mathrm{~Hz}$, when it is $400 \mathrm{~m}$ away from the crossing. The speed of sound in air is $340 \mathrm{~ms}^{-}$ ${ }^{1}$. The frequency of the second heard by a person standing on a road perpendicular to the track at a distance of $300 \mathrm{~m}$ from the crossing is

173097 A radar sends a radio signal of frequency $9 \times 10^{9}$ $\mathrm{Hz}$ towards an aircraft approaching the radar. If the reflected wave shows a frequency shift of $3 \times 10^{8} \mathrm{~Hz}$, the speed with which the aircraft is approaching the radar, in $\mathrm{m} / \mathrm{s}$ :
(Velocity of the radio signal is $3 \times 10^{8} \mathrm{~ms}^{-1}$

173098 One train is approaching an observer at rest and another train is receding him with same velocity $4 \mathrm{~m} / \mathrm{s}$. Both the trains blow whistles of same frequency of $243 \mathrm{~Hz}$ The beat frequency in $\mathrm{Hz}$ as heard by the observer is:
(Speed of sound in air $=320 \mathrm{~m} / \mathrm{s}$ )

173100 An observer moves towards a stationary source of sound with a velocity one-fourth of the velocity of sound. The percentage increase in apparent frequency is

173094 A train approaching a railway crossing at a speed of $180 \mathrm{kmh}^{-1}$ sounds a short whistle at a frequency $600 \mathrm{~Hz}$, when it is $400 \mathrm{~m}$ away from the crossing. The speed of sound in air is $340 \mathrm{~ms}^{-}$ ${ }^{1}$. The frequency of the second heard by a person standing on a road perpendicular to the track at a distance of $300 \mathrm{~m}$ from the crossing is

173097 A radar sends a radio signal of frequency $9 \times 10^{9}$ $\mathrm{Hz}$ towards an aircraft approaching the radar. If the reflected wave shows a frequency shift of $3 \times 10^{8} \mathrm{~Hz}$, the speed with which the aircraft is approaching the radar, in $\mathrm{m} / \mathrm{s}$ :
(Velocity of the radio signal is $3 \times 10^{8} \mathrm{~ms}^{-1}$

173098 One train is approaching an observer at rest and another train is receding him with same velocity $4 \mathrm{~m} / \mathrm{s}$. Both the trains blow whistles of same frequency of $243 \mathrm{~Hz}$ The beat frequency in $\mathrm{Hz}$ as heard by the observer is:
(Speed of sound in air $=320 \mathrm{~m} / \mathrm{s}$ )

173100 An observer moves towards a stationary source of sound with a velocity one-fourth of the velocity of sound. The percentage increase in apparent frequency is

173094 A train approaching a railway crossing at a speed of $180 \mathrm{kmh}^{-1}$ sounds a short whistle at a frequency $600 \mathrm{~Hz}$, when it is $400 \mathrm{~m}$ away from the crossing. The speed of sound in air is $340 \mathrm{~ms}^{-}$ ${ }^{1}$. The frequency of the second heard by a person standing on a road perpendicular to the track at a distance of $300 \mathrm{~m}$ from the crossing is

173097 A radar sends a radio signal of frequency $9 \times 10^{9}$ $\mathrm{Hz}$ towards an aircraft approaching the radar. If the reflected wave shows a frequency shift of $3 \times 10^{8} \mathrm{~Hz}$, the speed with which the aircraft is approaching the radar, in $\mathrm{m} / \mathrm{s}$ :
(Velocity of the radio signal is $3 \times 10^{8} \mathrm{~ms}^{-1}$

173098 One train is approaching an observer at rest and another train is receding him with same velocity $4 \mathrm{~m} / \mathrm{s}$. Both the trains blow whistles of same frequency of $243 \mathrm{~Hz}$ The beat frequency in $\mathrm{Hz}$ as heard by the observer is:
(Speed of sound in air $=320 \mathrm{~m} / \mathrm{s}$ )

173100 An observer moves towards a stationary source of sound with a velocity one-fourth of the velocity of sound. The percentage increase in apparent frequency is

173094 A train approaching a railway crossing at a speed of $180 \mathrm{kmh}^{-1}$ sounds a short whistle at a frequency $600 \mathrm{~Hz}$, when it is $400 \mathrm{~m}$ away from the crossing. The speed of sound in air is $340 \mathrm{~ms}^{-}$ ${ }^{1}$. The frequency of the second heard by a person standing on a road perpendicular to the track at a distance of $300 \mathrm{~m}$ from the crossing is

173097 A radar sends a radio signal of frequency $9 \times 10^{9}$ $\mathrm{Hz}$ towards an aircraft approaching the radar. If the reflected wave shows a frequency shift of $3 \times 10^{8} \mathrm{~Hz}$, the speed with which the aircraft is approaching the radar, in $\mathrm{m} / \mathrm{s}$ :
(Velocity of the radio signal is $3 \times 10^{8} \mathrm{~ms}^{-1}$

173098 One train is approaching an observer at rest and another train is receding him with same velocity $4 \mathrm{~m} / \mathrm{s}$. Both the trains blow whistles of same frequency of $243 \mathrm{~Hz}$ The beat frequency in $\mathrm{Hz}$ as heard by the observer is:
(Speed of sound in air $=320 \mathrm{~m} / \mathrm{s}$ )

173100 An observer moves towards a stationary source of sound with a velocity one-fourth of the velocity of sound. The percentage increase in apparent frequency is