Why do boats float instead of sink?

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When an object is first put into water, it pushes down with a certain amount of force to move the water aside and make room for itself. (Think about getting into the bathtub: the water rises because it has moved aside to make room for you to be inside the tub with it.)

But at the same time an object is pushing down against the water it is in, the water is trying to push back up against the object! – The trick to floating is when there’s enough water for the object’s weight and size so that the water pushes up with the more force than the object pushes down! Boats float because they’ve been built in a special way that allows them to push down against the water just as much as the water pushes up against them!

Calling all young skippers! (And their parents)

Find or make two objects that are of different sizes or shapes, but have the same weight. For example, you can use two empty aluminum cans -- one which has been crushed down and compacted, and the other which has not. Fill up a sink or large bowl with water and put each can in the water, one at a time.

Which one floats? Do you know why??

Posted by  Anjali25  on 2011-02-21 17:16:32  

My boy LOVES LOVES LOVES boats. We'll be doing a lot of reading from here =)