Which statement correctly describes Archimedes' principle?

Which statement correctly describes Archimedes' principle?

• A. Buoyant force equals weight of the object
• B. Buoyant force equals weight of the displaced fluid
• C. Buoyant force equals atmospheric pressure acting on the object
• D. Buoyant force equals the density of the fluid times the volume of displaced fluid

Answer: (B)

Archimedes' principle says the buoyant force on a body in a fluid equals the weight of the fluid it displaces. This comes from the way fluid pressure acts: pressure increases with depth, so the pressure pushing up from below is greater than the pressure pushing down from above, producing a net upward force. That upward force is equal to the weight of the displaced fluid, which can be written as F_b = ρ_fluid · g · V_displaced. So the statement that buoyant force equals the weight of the displaced fluid is the correct description. The other ideas miss key pieces: buoyant force is not simply the weight of the object, though that balance determines floating vs sinking; atmospheric pressure is not what sets the net buoyant force; and density times volume gives mass of displaced fluid, not its weight (which requires multiplying by g).

Archimedes' principle says the buoyant force on a body in a fluid equals the weight of the fluid it displaces. This comes from the way fluid pressure acts: pressure increases with depth, so the pressure pushing up from below is greater than the pressure pushing down from above, producing a net upward force. That upward force is equal to the weight of the displaced fluid, which can be written as F_b = ρ_fluid · g · V_displaced.

So the statement that buoyant force equals the weight of the displaced fluid is the correct description. The other ideas miss key pieces: buoyant force is not simply the weight of the object, though that balance determines floating vs sinking; atmospheric pressure is not what sets the net buoyant force; and density times volume gives mass of displaced fluid, not its weight (which requires multiplying by g).