JEE Main 2016 · 9 Apr · Shift 1 · Physics Q11

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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 :

450 Hz

540 Hz

648 Hz

270 Hz

Answer and worked solution

Official answer: C

Source and observer approach each other at 30 m/s each:
$f'=540\times\frac{330+30}{330-30}=648\text{ Hz}.$

Topics:Doppler effect

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JEE Main 2016 · 9 Apr · Shift 1, Physics question 11