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A Levels Physics (9702)•9702/11/M/J/19
Question 12 from 9702/11/M/J/19

Explanation

Archimedes' Principle for Floating Iceberg

Steps:

  • Weight of iceberg equals buoyant force: ρ_i g (π r² H) = ρ_w g [π r² (H - h)].
  • Cancel common terms: ρ_i H = ρ_w (H - h).
  • Rearrange: ρ_w h = ρ_w H - ρ_i H.
  • Solve: h = H (ρ_w - ρ_i)/ρ_w.

Why A is correct:

  • Matches the equilibrium condition from Archimedes' principle, where h is the unsubmerged fraction proportional to the density difference.

Why the others are wrong:

  • B: Represents submerged height fraction ρ_i/ρ_w, not above-water height.
  • C: Exceeds H since ρ_w > ρ_i, impossible for floating object.
  • D: Identical to B, incorrectly gives submerged fraction.

Final answer: A

Topic: Density and pressure

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