A person observes two moving trains, ‘A’ reaching the station and ‘B’ leaving the station with equal speed of 30 m s⁻¹. If both trains emit sounds with frequency 300 Hz, (Speed of sound: 330 m s⁻¹) 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⁻¹. If both trains emit sounds with frequency 300 Hz, (Speed of sound: 330 m s⁻¹) approximate difference of frequencies heard by the person will be:

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G1 Physics · Accepted Answer

Step 1: For the approaching train, f₁=300×330/(330−30)=330 Hz. For the receding train, f₂=300×330/(330+30)=275 Hz. Step 2: Difference = 55 Hz. Final: B.