172929 A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $400 \mathrm{~Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=\mathbf{3 6 0}$ $\mathrm{ms}^{-1}$ ]
172933 Two trains $A$ and $B$ are moving towards each other with speeds $72 \mathrm{kmh}^{-1}$ and $36 \mathrm{kmh}^{-1}$ respectively. The train-A whistles at $640 \mathrm{~Hz}$ frequency. Before the trains meet, frequency of sound heard by a passenger in Train-B is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )
172934 A police car moving at $5.4 \mathrm{~km} / \mathrm{hr}$ sounds siren emitting frequency of $550 \mathrm{~Hz}$ which is reflected back from a stationary object some distance ahead of the car. The number of beats heard per second by an observer sitting in the car is (Assume velocity of sound in air $=330 \mathrm{~m} / \mathrm{sec}$ )
172929 A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $400 \mathrm{~Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=\mathbf{3 6 0}$ $\mathrm{ms}^{-1}$ ]
172933 Two trains $A$ and $B$ are moving towards each other with speeds $72 \mathrm{kmh}^{-1}$ and $36 \mathrm{kmh}^{-1}$ respectively. The train-A whistles at $640 \mathrm{~Hz}$ frequency. Before the trains meet, frequency of sound heard by a passenger in Train-B is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )
172934 A police car moving at $5.4 \mathrm{~km} / \mathrm{hr}$ sounds siren emitting frequency of $550 \mathrm{~Hz}$ which is reflected back from a stationary object some distance ahead of the car. The number of beats heard per second by an observer sitting in the car is (Assume velocity of sound in air $=330 \mathrm{~m} / \mathrm{sec}$ )
172929 A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $400 \mathrm{~Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=\mathbf{3 6 0}$ $\mathrm{ms}^{-1}$ ]
172933 Two trains $A$ and $B$ are moving towards each other with speeds $72 \mathrm{kmh}^{-1}$ and $36 \mathrm{kmh}^{-1}$ respectively. The train-A whistles at $640 \mathrm{~Hz}$ frequency. Before the trains meet, frequency of sound heard by a passenger in Train-B is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )
172934 A police car moving at $5.4 \mathrm{~km} / \mathrm{hr}$ sounds siren emitting frequency of $550 \mathrm{~Hz}$ which is reflected back from a stationary object some distance ahead of the car. The number of beats heard per second by an observer sitting in the car is (Assume velocity of sound in air $=330 \mathrm{~m} / \mathrm{sec}$ )
172929 A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $400 \mathrm{~Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=\mathbf{3 6 0}$ $\mathrm{ms}^{-1}$ ]
172933 Two trains $A$ and $B$ are moving towards each other with speeds $72 \mathrm{kmh}^{-1}$ and $36 \mathrm{kmh}^{-1}$ respectively. The train-A whistles at $640 \mathrm{~Hz}$ frequency. Before the trains meet, frequency of sound heard by a passenger in Train-B is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )
172934 A police car moving at $5.4 \mathrm{~km} / \mathrm{hr}$ sounds siren emitting frequency of $550 \mathrm{~Hz}$ which is reflected back from a stationary object some distance ahead of the car. The number of beats heard per second by an observer sitting in the car is (Assume velocity of sound in air $=330 \mathrm{~m} / \mathrm{sec}$ )
172929 A car $P$ travelling at $20 \mathrm{~ms}^{-1}$ sounds its horn at a frequency of $400 \mathrm{~Hz}$. Another car $Q$ is travelling behind the first car in the same direction with a velocity $40 \mathrm{~ms}^{-1}$. The frequency heard by the passenger of the car $Q$ is approximately [Take, velocity of sound $=\mathbf{3 6 0}$ $\mathrm{ms}^{-1}$ ]
172933 Two trains $A$ and $B$ are moving towards each other with speeds $72 \mathrm{kmh}^{-1}$ and $36 \mathrm{kmh}^{-1}$ respectively. The train-A whistles at $640 \mathrm{~Hz}$ frequency. Before the trains meet, frequency of sound heard by a passenger in Train-B is (Speed of sound in air $=340 \mathrm{~ms}^{-1}$ )
172934 A police car moving at $5.4 \mathrm{~km} / \mathrm{hr}$ sounds siren emitting frequency of $550 \mathrm{~Hz}$ which is reflected back from a stationary object some distance ahead of the car. The number of beats heard per second by an observer sitting in the car is (Assume velocity of sound in air $=330 \mathrm{~m} / \mathrm{sec}$ )