Two passenger trains moving with a speed of 108 km/hour cross each other. One of them blows a whistle whose frequency is 750 Hz. If sound speed is 330 m/s, then passengers sitting in the other train, after trains cross each other will hear sound whose frequency will be [MP PMT 1991]

900 Hz

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625 Hz

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750 Hz

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800 Hz

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Solution

The correct option is B 625 Hz
$n^{'} = n (\frac{v - v_{0}}{v + v_{s}}) = 750 (\frac{330 - 180 \times \frac{5}{18}}{330 + 180 \times \frac{5}{18}}) = 625$ Hz

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Two passenger trains moving with a speed of 108 km/hour cross each other. One of them blows a whistle whose frequency is 750 Hz. If sound speed is 330 m/s, then passengers sitting in the other train, after trains cross each other will hear sound whose frequency will be [MP PMT 1991]

The correct option is B 625 Hzn′=n(v−v0v+vs)=750(330−180×518330+180×518)=625 Hz

The correct option is B 625 Hz
$n^{'} = n (\frac{v - v_{0}}{v + v_{s}}) = 750 (\frac{330 - 180 \times \frac{5}{18}}{330 + 180 \times \frac{5}{18}}) = 625$ Hz