Buoyancy and Density

Why do boats float on water? Today, or maybe it was yesterday, a friend asked me why does boats float on water. My first answer was that it has to do with the density of the implicated objects. I was quite sure about my answer. Certainly it has to do with density, but another friend reminded me about Archimedes´ principle.

Archimedes of Syracuse (287-212 BC) is very known because of his discoveries and inventions, you may read more about him on wikipedia.

"He stepped into a bath and noticed that the water level rose – he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged and... Eureka!!". Now could the volume of irregular objects be calculated with precision. He also realized that the sumerged objects were afected by a force that pushed them up. This force is called buoyant force.


So we say that:

"The buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object"

Take a look at the following video, it explains very clearly the whole science behind my firend´s question. Density and bouyant force and why do boats float and a lot of other phenomenas are described in it. So WATCH IT!!