L A F O T or art by Creston Ely
Which things will float and which will sink?
You might think that big, heavy things sink, and smaller, lighter ones float. An orange is bigger and heavier than a paper clip.
And if you make the orange smaller and lighter by taking off its peel, what happens?
But look. The orange floats and the paper clip sinks!
Big things can float when they are less dense than water. That means they weigh less than water in the exact same size and shape would weigh.
The orange’s peel weighs much less than a ribbon of water the same size would. It is less dense than water, so it floats too.
The whole orange floats because it weighs less than a ball of water the same size would. It is less dense than water.
Without the peel, the juicy fruit inside weighs more than a ball of water the same size would. It is denser than water, so it sinks.
A paper clip is made of metal. Metal is denser than water, so it sinks. But what about big boats? They are made of metal. Why don’t they sink? 10
The peel acts like a life jacket for the fruit inside.
Whenever you put an object in water, it pushes the water away to make room for itself. See for yourself. Fill a small bowl all the way to the top with water. Now put an orange into the bowl. The water the orange pushes away spills out of the bowl.
Make sure you have something to catch the water.
The orange isn’t the only thing that pushes. Water pushes too. Try pushing an empty plastic bottle down under water. Can you feel the water pushing back?
If you let go of the bottle, the water pushes it right back up.
I should have brought an umbrella!
When something weighs more than the amount of water it pushes away, it sinks. Sometimes you can make it push away more water by changing its shape. If you can make it push away enough water, it will float.
See for yourself. Mark the water level on a glass of water.
Roll a lump of clay into a ball, and put it in the glass. Mark how high the water level is now.
The ball pushes away water, so the water level rises.
But the ball is heavier than the amount of water it pushes away, so the ball sinks.
Take the ball out, and form it into a boat shape. The clay should float now. (If your boat doesn’t float, try making the sides higher.) Now how high does the water rise? The boat weighs the same as the ball, but it pushes away more water.
The more water that gets pushed away, the harder the water pushes back. The water pushes back so hard that the boat floats.
Let’s see how high we can make the water rise.