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JEE Main 2022 (25 Jul, Shift 1) · Newton's Law of Gravitation

Newton's Law of Gravitation question from JEE Main 2022 (25 Jul, Shift 1)

Q13JEE Main 2022 · 25 JUL · SHIFT 1Difficult

Newton's Law of Gravitation

Three identical particles A,BA, B and CC of mass 100 kg100\text{ kg} each are placed in a straight line with AB=BC=13 mAB = BC = 13\text{ m}. The gravitational force on a fourth particle PP of the same mass is FF, when placed at a distance 13 m13\text{ m} from the particle BB on the perpendicular bisector of the line ACAC. The value of FF will be approximately:

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Answer: (b)

ABCP13 m13 m13√2 m
  1. B pulls PP from 1313 m: FB=G(100)2169≈59.2GF_B = \frac{G(100)^2}{169} \approx 59.2G.
  2. A and C are at 13213\sqrt{2} m: each G(100)2338≈29.6G\frac{G(100)^2}{338} \approx 29.6G, at 45∘45^\circ to PBPB.
  3. Sideways parts cancel; along PBPB: 2×29.6Gcos⁡45∘≈41.8G2 \times 29.6G \cos45^\circ \approx 41.8G.
  4. F≈59.2G+41.8G≈101GF \approx 59.2G + 41.8G \approx 101G
  5. So the answer is (b) 100G100G.
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