A person observes two moving trains, A reaching the station and B leaving the station with equal speed of 30 m/s. If both trains emit sounds with frequency 300 Hz, (speed of sound = 330 m/s) approximate difference of frequencies heard by the person will be:
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Question

A person observes two moving trains, A reaching the station and B leaving the station with equal speed of 30 m/s. If both trains emit sounds with frequency 300 Hz, (speed of sound = 330 m/s) approximate difference of frequencies heard by the person will be:

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G1 Physics · Accepted Answer

For the approaching train, f₁ = f[v/(v−vₛ)] = 300×330/300 = 330 Hz. For the receding train, f₂ = f[v/(v+vₛ)] = 300×330/360 = 275 Hz. Difference = 55 Hz.