I have no idea how it is possible that a boat floats. Some of them are made with concrete, or metal, and other heavy material that on their own would sink, regardless of shape. But somehow, when it’s used to build a boat, it floats just as fine even if it carries extremely heavy load.
So what is the science behind boat floating, but explained to me like I’m five? 🙂
In: Engineering
Objects have buoyancy in different substances. This is caused by density (weight versus volume). Water has a density of about 1 kg/L ( 1L of water weighs 1 kg; you can fit 1 kg of substance in 1 L of space). Anything that is *more* dense than water (i.e. 1 L of it weighs more than 1 kg) will sink. Anything that is less dense will float.
Now, I’m sure you’re thinking “concrete, metal- all these things are *way* more dense than water” which is true. But boats use something very important: air.
The shape of a boat means that you end up having air underneath the waterline. Air has a density of 1.29 g/L (0.00129 kg/L). So although metal is more dense than water, you have to think about the density of the boat as a whole. That section of the boat that is at and under the waterline is *less* dense than water because its shape allows air between it.
If you’ve ever had a mug in a full sink, it’s the same principle.
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