|MadSci Network: Physics|
The buoyancy is inversely proportional to the density, with the less dense material being more buoyant. Cork has a density of between 0.22 and 0.26 grams per cubic centimeter (Smithsonian Physical Tables, Smithsonian Institution Press), while styrofoam has a wider range of densities depending on the type of styrofoam and its intended use. For styrofoam typical densities are between 0.03 and 0.12 grams per cubic centimeter (source: various Web pages). So, sytrofoam is, in general, more buoyant than cork.
John Link, MadSci Physicist
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