Archimedes' principle relates buoyant force to the weight of displaced fluid.

• A. The volume of the object
• B. The weight of displaced fluid
• C. The density of the fluid
• D. The surface area of the object

Answer: (B)

Buoyant force comes from pushing aside fluid; Archimedes' principle says that upward force on a submerged object equals the weight of the fluid it displaces. That weight is the fluid’s density times the displaced volume times gravity. So for a given submerged portion, the buoyant force depends on how much fluid is moved and how heavy that fluid is. The volume of the object alone doesn’t determine buoyancy—what matters is the volume of fluid displaced, which is tied to how much of the object is underwater. The density of the fluid affects the magnitude (denser fluid means heavier displaced fluid), but you still need the displaced volume. The surface area doesn’t directly set the buoyant force. Therefore, the buoyant force is best described by the weight of the displaced fluid.