JEE Mains · Physics · STD 11 - 14. waves and sound
The driver of a bus approaching a big wall notices that the frequency of his bus's horn changes from \(420\, Hz\) to \(490\, Hz ,\) when he hears it after it gets reflected from the wall. Find the speed of the bus (in \(kmh^{-1}\)) if speed of the sound is \(330\, ms ^{-1}\).
- A \(91\)
- B \(71\)
- C \(81\)
- D \(61\)
Answer & Solution
Correct Answer
(A) \(91\)
Step-by-step Solution
Detailed explanation
\(f _{1}=\left(\frac{330}{330- v _{ B }}\right) 420\) \(f _{2}=\left(\frac{330+ v _{0}}{330}\right)\left(\frac{330}{330- v _{ B }}\right) 420\) \(490=\left(\frac{330+ v _{ B }}{330- v _{ B }}\right) 420\) \(\frac{7}{6}=\frac{330+ v _{ B }}{330- v _{ B }}\)…
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