Cargo Ships Float

Why do cargo ships float?
- Teri Navarro (age 13)
Corinth, Ms, Alcorn

Teri- Things float as long as the water they displace (move out of the way) weighs as much as they do. Whether that happens depends on the density of the thing. The density of an object is equal to its weight divided by its volume. Every substance, including water, has its own density at a given temperature (density can vary as a substance gets hotter or colder). Any substance that is less dense than water floats while one that is more dense sinks. However, even though cargo ships hold a ton of heavy cargo, they have chambers of air inside that make them mostly hollow. This brings me to the main point... an object that is hollow like a cargo ship floats if its density-its weight divided by its total volume is less than the density of water. Thanks for your question! -Kim-

(published on 10/22/2007)