A) \[15\sqrt{2}m{{s}^{-1}}\]
B) \[15/\sqrt{2}m{{s}^{-1}}\]
C) \[15m{{s}^{-1}}\]
D) \[30\,m{{s}^{-1}}\]
Correct Answer: C
Solution :
Velocity of sound in air = 300 m/s. If a source of sound is moving towards a stationary listener, the frequency heard by the listener would be different from the actual frequency of the source, this apparent frequency is given by \[{{f}_{app}}=\left( \frac{{{v}_{sound\,in\,air}}}{{{v}_{sound\,in\,air}}\pm {{V}_{source}}} \right),\]where symbols have their usual meanings. In the denominator +ve sign would be taken when source is receding away from the listener, while ?ve sign would be taken when source is approaching the listener. Let v be the maximum value of source velocity for which the person is able to hear the sound, then \[10000=\left( \frac{300}{300-v} \right)\times 9500\] \[\Rightarrow \] \[v=15\,m/s\]
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