Final answer:
An object's density can be calculated using its weight in air and its apparent weight when submerged in a fluid, based on Archimedes' principle.
Step-by-step explanation:
An object, such as a coin, is weighed in air and then weighed again while submerged in a liquid. This technique can be used to calculate the density of the object if the fluid density is known. It is based on Archimedes' principle, which states that the buoyant force on an object equals the weight of the fluid displaced. The object's apparent weight, or the weight it appears to have when submerged, is equal to its actual weight minus the weight of the fluid it displaces.