A sound wave of wavelength λ travels towards the right horizontally with a velocity v. It strikes and reflects from a vertical plane surface, travelling at acceleration a starting from rest. The number of positive crests striking in a time interval of 5 s on the wall is
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Question

A sound wave of wavelength λ travels towards the right horizontally with a velocity v. It strikes and reflects from a vertical plane surface, travelling at acceleration a starting from rest. The number of positive crests striking in a time interval of 5 s on the wall is

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G1 Physics · Accepted Answer

Step 1: For y = A sin(ωt ± kx + φ), particle velocity is u = ∂y/∂t and acceleration is a = ∂²y/∂t² = −ω²y. Step 2: Use u² = ω²(A² − y²) when only displacement is known. Step 3: Use the graph/slope to fix the sign. Final: A: 5(v + 5a/2)/λ.