Buoyancy equilibrium for floating pipe

Steps:

• Weight of pipe equals buoyant force: 32 N = ρ × g × V_displaced.
• V_displaced = cross-sectional area × submerged length = 0.12 m² × 0.03 m = 0.0036 m³ (submerged length from diagram).
• Substitute g = 9.8 m/s²: 32 = ρ × 9.8 × 0.0036.
• Solve for ρ: ρ = 32 / (9.8 × 0.0036) ≈ 907 kg/m³, which rounds to 910 kg/m³.

Why B is correct:

• Matches Archimedes' principle: buoyant force = weight of displaced liquid, yielding ρ = 910 kg/m³ for given area and submerged length.

Why the others are wrong:

• A: Assumes longer submerged length (~0.04 m), overestimating volume displaced.
• C: Assumes very short submerged length (~0.004 m), underestimating volume and overestimating density.
• D: Assumes even shorter submerged length (~0.003 m), further underestimating volume.

Final answer: B