# physics

15 beats are heard in 5 seconds when a piano key and a tuning fork of slightly higher frequency (440 Hz) are struck at the same time. What is the frequency of the sound emitted by the piano key?

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1. 440-f=15

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2. Number of beats heard per second = 15/5 = 3 beats/sec. We know number of beats heard per second = difference in frequency of the two sound waves. So 3 = 440 - fp, where fp is the frequency of the piano key which is slightly lower than 440 Hz. Solving for fp, we get fp = 337 Hz.

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3. 337

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