A) 9.7 s
B) 10.2 s
C) 6.7 s
D) 5.8 s
E) 3.7 s
Correct Answer: A
Solution :
The apparent frequency \[=n\times \frac{v+{{v}_{a}}-{{v}_{0}}}{v+{{v}_{a}}-{{v}_{s}}}\] Here \[n=\] frequency and \[{{v}_{a}}=\]velocity of air Let\[T\]and\[T\]be the the apparent time periods Then \[T=\frac{1}{n}\]and \[T=\frac{1}{n}\] \[\therefore \] \[\frac{1}{T}=\frac{1}{T}\times \frac{v+a-{{v}_{0}}}{v+a-{{v}_{s}}}\] \[\Rightarrow \] \[T=T\times \left( \frac{v+{{v}_{a}}-{{v}_{s}}}{v+{{v}_{a}}-{{v}_{0}}} \right)\] \[\Rightarrow \] \[T=10\times \left( \frac{340+20-10}{340+20} \right)\]\[(\because \,{{v}_{0}}=0)\] \[=\frac{10\times 350}{360}=\frac{350}{36}=9.7s\]You need to login to perform this action.
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