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Why does wood float? |
by Mya Kagan (whyzz writer) >> more about the author
If you’ve ever seen a plank of wood or even an entire log floating along a river, then you’ve probably wondered how and why this happens!
When something like a log of wood is put into water, it pushes down on the water and the water moves aside to make room for the object. (Think, for example, of how the water in the bathtub moves aside and makes room for you when you step into the tub!) When there is enough water to push back up against the object with the same force as the object is pushing down, then the object will float!
That’s why a piece of wood that is lightweight for its size will float in a big body of water, like the ocean or a river. However, that same piece of wood might not float in a different smaller body of water, such as your swimming pool or tub!
Floating Fun!
Have a grown-up help you fill a small tub or sink with some water and test out objects that float versus objects that sink!
Try things such as stones, plastic toys, a metal spoon, and a rubber ball. Think about the weight and size of each object and make a guess about whether or not it will float! How many are you able to guess correctly??
When something like a log of wood is put into water, it pushes down on the water and the water moves aside to make room for the object. (Think, for example, of how the water in the bathtub moves aside and makes room for you when you step into the tub!) When there is enough water to push back up against the object with the same force as the object is pushing down, then the object will float!
That’s why a piece of wood that is lightweight for its size will float in a big body of water, like the ocean or a river. However, that same piece of wood might not float in a different smaller body of water, such as your swimming pool or tub!
- The word “density” is often used to refer to how heavy something is for its size. If you had two pieces of wood the same size but one was heavier than the other, you could say that the heavier one was more dense.
- The reason why wood often has low density is because it contains a lot of airy space. However, sometimes a piece of wood can become so wet (for example, if it spends a really long time in the water) that it will end up sinking.
Floating Fun!
Have a grown-up help you fill a small tub or sink with some water and test out objects that float versus objects that sink!
Try things such as stones, plastic toys, a metal spoon, and a rubber ball. Think about the weight and size of each object and make a guess about whether or not it will float! How many are you able to guess correctly??
