Buoyancy is the difference between floating and sinking, or staying in the middle.  When you drop a ball full of air into the water it normally floats, that’s because  the buoyancy force is stronger than the weight of the ball.  If you drop a ball that has no air inside it into the water it will sink.  This is because the weight of the ball in stronger than the buoyancy force, so it sinks.  If you drop a ball that has a bit of air inside into the water it will float in the middle. This is because the forces are both the same.

A man and a lady came into our school and talked to us about buoyancy, we made little divers out of white tack; a bottle of water and a little tube that water can go inside.  If you add lots of white tack it will sink in the bottle of water, that is because it is too buoyant.  If you take some off it will make it float. Once it is floating you can squeeze the bottle and the diver will go down.  When you let go will go back up, we tried to make it stay in the middle.  It was really fun learning about buoyancy and I would like to learn some more.

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