Final answer:
An object will float if its average density is less than that of the surrounding fluid, as explained by Archimedes' Principle. The buoyant force must be greater than the weight of the object for it to stay afloat.
Step-by-step explanation:
In order for an object to float, its average density must be less than the density of the surrounding fluid. This is explained by Archimedes' Principle, which states that an object will float if the buoyant force, which is equal to the weight of the fluid displaced by the object, is greater than the weight of the object itself. For example, if a block of wood and a block of brass have the same mass, the wood floats and the brass sinks when placed in water because wood has a lower density than water, whereas brass has a higher density than water. The density of an object is determined by its mass divided by its volume, and this relationship is crucial when estimating whether an object will float or sink.