Which principle explains why objects float or sink in a fluid?

Archimedes' Principle provides the fundamental understanding of buoyancy, explaining why objects either float or sink when placed in a fluid. This principle states that an object submerged in a fluid experiences an upward buoyant force that is equal to the weight of the fluid displaced by the object. When the upward buoyant force is greater than the weight of the object, the object will float. Conversely, if the object's weight exceeds the buoyant force, it will sink.

This principle relates directly to the concepts of density and displacement. An object with a density lower than that of the fluid will displace a volume of fluid equal to its weight before it is fully submerged, leading it to float. In contrast, an object with a higher density than the fluid will displace less fluid than its own weight, thus sinking.

Understanding Archimedes’ Principle is essential for analyzing various phenomena involving buoyancy in different fluids, making it a key concept in physical science.