172969 Two trains are moving towards each other with speeds of $20 \mathrm{~m} / \mathrm{s}$ and $15 \mathrm{~m} / \mathrm{s}$ relative to the ground. The first train sounds a whistle of frequency $600 \mathrm{~Hz}$. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is $340 \mathrm{~m} / \mathrm{s}$ )

172970 A police car moving at $22 \mathrm{~ms}^{-1}$ chases a motor cyclist. The police man sounds horn at $176 \mathrm{~Hz}$, while both of them move towards a stationary siren of frequency $165 \mathrm{~Hz}$. If the number of beats heard by the motor cyclist per second is zero, then the speed of motorcycle is (Speed of sound in air $=330 \mathrm{~ms}^{-1}$ )

172971 A source producing sound of frequency $720 \mathrm{~Hz}$ is falling freely from the top of a tower of height $20 \mathrm{~m}$. The frequency of sound heard by an observer on the top of the tower when the source just reaches the ground is (Acceleration due to gravity, $g=10 \mathrm{~ms}^{-2}$ and speed of sound in air $=\mathbf{3 4 0} \mathbf{~ m s}^{-1}$ )

172972 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{h}$ sounds a whistle of frequency $576 \mathrm{~Hz}$, when it is $288 \mathrm{~m}$ away from the crossing. The frequency heard by the observer standing on the road perpendicular to the track from the crossing at a distance of $384 \mathrm{~m}$ is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )

172969 Two trains are moving towards each other with speeds of $20 \mathrm{~m} / \mathrm{s}$ and $15 \mathrm{~m} / \mathrm{s}$ relative to the ground. The first train sounds a whistle of frequency $600 \mathrm{~Hz}$. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is $340 \mathrm{~m} / \mathrm{s}$ )

172970 A police car moving at $22 \mathrm{~ms}^{-1}$ chases a motor cyclist. The police man sounds horn at $176 \mathrm{~Hz}$, while both of them move towards a stationary siren of frequency $165 \mathrm{~Hz}$. If the number of beats heard by the motor cyclist per second is zero, then the speed of motorcycle is (Speed of sound in air $=330 \mathrm{~ms}^{-1}$ )

172971 A source producing sound of frequency $720 \mathrm{~Hz}$ is falling freely from the top of a tower of height $20 \mathrm{~m}$. The frequency of sound heard by an observer on the top of the tower when the source just reaches the ground is (Acceleration due to gravity, $g=10 \mathrm{~ms}^{-2}$ and speed of sound in air $=\mathbf{3 4 0} \mathbf{~ m s}^{-1}$ )

172972 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{h}$ sounds a whistle of frequency $576 \mathrm{~Hz}$, when it is $288 \mathrm{~m}$ away from the crossing. The frequency heard by the observer standing on the road perpendicular to the track from the crossing at a distance of $384 \mathrm{~m}$ is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )

172969 Two trains are moving towards each other with speeds of $20 \mathrm{~m} / \mathrm{s}$ and $15 \mathrm{~m} / \mathrm{s}$ relative to the ground. The first train sounds a whistle of frequency $600 \mathrm{~Hz}$. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is $340 \mathrm{~m} / \mathrm{s}$ )

172970 A police car moving at $22 \mathrm{~ms}^{-1}$ chases a motor cyclist. The police man sounds horn at $176 \mathrm{~Hz}$, while both of them move towards a stationary siren of frequency $165 \mathrm{~Hz}$. If the number of beats heard by the motor cyclist per second is zero, then the speed of motorcycle is (Speed of sound in air $=330 \mathrm{~ms}^{-1}$ )

172971 A source producing sound of frequency $720 \mathrm{~Hz}$ is falling freely from the top of a tower of height $20 \mathrm{~m}$. The frequency of sound heard by an observer on the top of the tower when the source just reaches the ground is (Acceleration due to gravity, $g=10 \mathrm{~ms}^{-2}$ and speed of sound in air $=\mathbf{3 4 0} \mathbf{~ m s}^{-1}$ )

172972 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{h}$ sounds a whistle of frequency $576 \mathrm{~Hz}$, when it is $288 \mathrm{~m}$ away from the crossing. The frequency heard by the observer standing on the road perpendicular to the track from the crossing at a distance of $384 \mathrm{~m}$ is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )

172969 Two trains are moving towards each other with speeds of $20 \mathrm{~m} / \mathrm{s}$ and $15 \mathrm{~m} / \mathrm{s}$ relative to the ground. The first train sounds a whistle of frequency $600 \mathrm{~Hz}$. The frequency of the whistle heard by a passenger in the second train before the train meets, is (the speed of sound in air is $340 \mathrm{~m} / \mathrm{s}$ )

172970 A police car moving at $22 \mathrm{~ms}^{-1}$ chases a motor cyclist. The police man sounds horn at $176 \mathrm{~Hz}$, while both of them move towards a stationary siren of frequency $165 \mathrm{~Hz}$. If the number of beats heard by the motor cyclist per second is zero, then the speed of motorcycle is (Speed of sound in air $=330 \mathrm{~ms}^{-1}$ )

172971 A source producing sound of frequency $720 \mathrm{~Hz}$ is falling freely from the top of a tower of height $20 \mathrm{~m}$. The frequency of sound heard by an observer on the top of the tower when the source just reaches the ground is (Acceleration due to gravity, $g=10 \mathrm{~ms}^{-2}$ and speed of sound in air $=\mathbf{3 4 0} \mathbf{~ m s}^{-1}$ )

172972 A train approaching a railway crossing at a speed of $120 \mathrm{~km} / \mathrm{h}$ sounds a whistle of frequency $576 \mathrm{~Hz}$, when it is $288 \mathrm{~m}$ away from the crossing. The frequency heard by the observer standing on the road perpendicular to the track from the crossing at a distance of $384 \mathrm{~m}$ is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )