A) \[40\,m{{s}^{-1}}\]
B) \[20\,m{{s}^{-1}}\]
C) \[34\,m{{s}^{-1}}\]
D) \[180\,m{{s}^{-1}}\]
Correct Answer: B
Solution :
From Doppler's effect received frequency \[\frac{9}{8}=\frac{340+{{V}_{s}}}{340-{{V}_{s}}}\,\left[ \because \,\,\frac{{{F}_{approach}}}{{{F}_{seperation}}}\,=\frac{\left( \frac{V}{V-{{V}_{S}}} \right)}{\left( \frac{V}{V+{{V}_{S}}} \right)}\,=\frac{V+{{V}_{S}}}{V-{{V}_{S}}}=\frac{9}{8} \right]\]\[\Rightarrow \,9(340-{{v}_{s}})\,=8\times (340\,+{{V}_{S}})\] \[{{V}_{S}}=\frac{340}{17}=20m{{s}^{-1}}\]You need to login to perform this action.
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