Two tuning forks A and B initially produce 5 beats per second. Wax is added only to fork B, lowering its frequency by 3 Hz, and the new beat frequency becomes 8 beats per second. Which statement must be true?
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Question

Two tuning forks A and B initially produce 5 beats per second. Wax is added only to fork B, lowering its frequency by 3 Hz, and the new beat frequency becomes 8 beats per second. Which statement must be true?

Options

G1 Physics · Accepted Answer

Initially, |f₂−f₁| = 5. Wax lowers the frequency of B by 3 Hz. The difference increases from 5 Hz to 8 Hz. This can happen only if B was already below A, because lowering B further increases the separation: f₁−f₂ = 5. After loading B, f₁−(f₂−3) = 8. Therefore fork B was initially 5 Hz below fork A. Correct option: A.