TS EAMCET · Physics · Waves and Sound
A car moving towards a cliff emits sound of frequency ' \(n\) '. If the difference in frequencies of the horn and its echo heard by the driver of the car is \(10 \%\) of ' \(n\) ', then the speed of the car is nearly (Speed of sound in air is \(336 \mathrm{~ms}^{-1}\) )
- A \(16 \mathrm{~ms}^{-1}\)
- B \(18 \mathrm{~ms}^{-1}\)
- C \(30 \mathrm{~ms}^{-1}\)
- D \(33 \mathrm{~ms}^{-1}\)
Answer & Solution
Correct Answer
(A) \(16 \mathrm{~ms}^{-1}\)
Step-by-step Solution
Detailed explanation
\( n'' = n \left( \frac{v + v_s}{v - v_s} \right) \) \( 1.1n = n \left( \frac{v + v_s}{v - v_s} \right) \) \( 1.1(v - v_s) = v + v_s \) \( 1.1v - 1.1v_s = v + v_s \) \( 0.1v = 2.1v_s \) \( v_s = \frac{0.1v}{2.1} = \frac{v}{21} \) \( v_s = \frac{336}{21} = 16 \mathrm{~ms}^{-1} \)
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