So, this mainly is about icebergs and how about 10% of them is above water but most of the iceberg sits below the water. I know that it has to do with the buoyancy and densities of water and ice, but I don’t really understand how part of it floats above the water. Thank you in advance!
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Answer: This is a great question because almost everything, when it is solid, does not float in itself. Ice is a very important exception.
When water freezes, it *expands*. This makes huge difference to our world. If ice sank, our lakes and oceans might never thaw out.
Every bit of ice wants to be by the surface because ice weighs less than water but weighs more than air. With big enough chunks of ice, not all of the ice can be on the surface due to the shape of an ice chunk. Some of the ice will be below the surface, and some above.
The ice under the surface will push the ice chunk upwards, and the ice above the surface will push the oce chunk downwards.
But the difference in weight (density) between ice and air is much bigger than the difference in weight between ice and water. Therefore we need a lot more ice below the water pushing the ice upwards to be able to match the ice above surface pushing it downwards.
When you put something that floats into water, it will displace an amount of fluid equal to its weight.
Let’s say that you have a 5 tonne iceberg. It will have a volume of 5.454m^(3). However, it can only displace 5 tonnes of water. 5 tonnes of water will displace 5m^(3). that means there is 0.454m^3 of iceberg that doesn’t displace any water, so you get that much floating above the surface of the water.
Archimedes principle states that an object experiences an upward force equivalent to the weight of the water it displaces. So an object that is less dense than water, like an iceberg, will float, because it can displace a a large volume of water relative to its weight. But it still needs to displace that water to float. That’s why most of the iceberg is still submerged. The iceberg will naturally reach equilibrium when it displaces an amount of water equal to its weight.
Ice is less dense than water, but only a tiny amount less dense. Wood might float with half the wood in the water that’s because wood is half as dense as water.
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