A submerged object experiences buoyant force according to Archimedes' principle. What is the magnitude of buoyant force?

A submerged object experiences buoyant force according to Archimedes' principle. What is the magnitude of buoyant force?

• A. F_b = ρ_fluid g V_submerged
• B. F_b = ρ_fluid g h
• C. F_b = m g
• D. F_b = ρ_submerged g V_submerged

Answer: (A)

The buoyant force comes from the fluid displaced by the object. Its strength equals the weight of that displaced fluid, so the magnitude is F_b = ρ_fluid g V_submerged, where ρ_fluid is the fluid density, g is gravity, and V_submerged is the volume of fluid pushed aside by the object. This ties directly to Archimedes’ principle: the upward push matches the weight of the displaced fluid. Other expressions don’t match the physics: ρ_fluid g h would give a pressure-like quantity rather than a total force without a specific area, m g is the weight of the object, and ρ_submerged g V_submerged would be the weight of the object’s material, not the displaced fluid. Hence the correct magnitude is F_b = ρ_fluid g V_submerged.

The buoyant force comes from the fluid displaced by the object. Its strength equals the weight of that displaced fluid, so the magnitude is F_b = ρ_fluid g V_submerged, where ρ_fluid is the fluid density, g is gravity, and V_submerged is the volume of fluid pushed aside by the object. This ties directly to Archimedes’ principle: the upward push matches the weight of the displaced fluid.

Other expressions don’t match the physics: ρ_fluid g h would give a pressure-like quantity rather than a total force without a specific area, m g is the weight of the object, and ρ_submerged g V_submerged would be the weight of the object’s material, not the displaced fluid. Hence the correct magnitude is F_b = ρ_fluid g V_submerged.