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NEET 2011 (AIPMT, Mains) · Periodic Motion & SHM Basics

Periodic Motion & SHM Basics question from NEET 2011 (AIPMT, Mains)

Q69NEET 2011 · AIPMT · MAINSMedium

Periodic Motion & SHM Basics

Two particles are oscillating along two close parallel straight lines side by side, with the same frequency and amplitudes. They pass each other, moving in opposite directions when their displacement is half of the amplitude. The mean positions of the two particles lie on a straight line perpendicular to the paths of the two particles. The phase difference is

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Answer: (c)

2π/3π/6P₁P₂level x = A/2 (dashed)x = 0
  1. At x=A2x = \frac{A}{2}: sin⁡ϕ=12\sin\phi = \frac{1}{2}, so ϕ=π6\phi = \frac{\pi}{6} or 5π6\frac{5\pi}{6}.
  2. Moving in opposite directions means one has cos⁡ϕ>0\cos\phi > 0 (π6\frac{\pi}{6}) and the other cos⁡ϕ<0\cos\phi < 0 (5π6\frac{5\pi}{6}).
  3. Δϕ=5π6−π6=2π3\Delta\phi = \frac{5\pi}{6} - \frac{\pi}{6} = \frac{2\pi}{3}
  4. So the answer is (c) 2π3\frac{2\pi}{3}.
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