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JEE Main 2016 (9 Apr, Shift 1) · Doppler Effect

Doppler Effect question from JEE Main 2016 (9 Apr, Shift 1)

Q61JEE Main 2016 · 9 APR · SHIFT 1Medium

Doppler Effect

Two engines pass each other moving in opposite directions with uniform speed of 30 m/s. One of them is blowing a whistle of frequency 540 Hz. Calculate the frequency heard by driver of second engine before they pass each other. Speed of sound is 330 m/sec:

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Answer: (c)

Before passing, both engines approach each other: $f' = f\,\dfrac{v + v_o}{v - v_s}$ .
$f' = 540 \times \dfrac{330 + 30}{330 - 30} = 540 \times \dfrac{360}{300}$
So the answer is (c) 648 Hz.

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