Why Does a Piece of Wood Float in Water?
A piece of wood will float in water because it is lighter than the same amount of water. We do not mean that a piece of wood weighing one pound, for instance, would weigh any more than a pound of water, of course, but if you took the measurements of each you will find that it took less bulk to make a pound of water than of wood. If you had a piece of wood so shaped that it just filled a glass completely, and then took another glass and filled it with water, you would find that the glass containing the water weighed the most. Another name to give to this difference would be to say that the water was more dense than the wood. By the law of gravitation the denser thing will always go to the bottom, and as wood is less dense than water, it will stay at the top if put in water. The piece of wood has more air in it than the water. If you could expel the air from the piece of wood and then put it in water, it would sink.