why does wood float?

Answer 1

as the density of wood is lower than that of water, it floats.

Answer 2

All the above are correct, if not simplistic. Perhaps you'd like to know more. Here it is....

f = ma = (W - B); where m = mass of the wood, a is its accleration in the water (up/down), W is the weight of the wood, and B is the buoyancy. As you can see, when the buoyancy equals the weight of the wood, there is no acceleration because net force f = 0 = ma.

Now here's the cool part. B = rho g V = rho g Ah; where rho is the mass density of the water, g = 9.81 m/sec^2 on Earth's surface, A is the cross sectional area of the wood bloc and displaced water, and h is the depth the wood sinks into the water. And if you look carefully at this, you will see that B is just the weight of the water displaced by the wood.

And there you have it. As f = ma = W - B, when the wood stops sinking; so that a = 0 its weight is equal to the weight of the water it displaces (the buoyancy). And of course, when it stops sinking we say it is floating. And that's why wood floats most of the time. The water it displaces when it settles into the water weighs as much as the wood does.

Look at the physics a bit. As B = rho g V = rho g Ah, would that wood sink further into the water if the water were denser? Or would it sink less deep? That is, where do the h's end up.

Just for fun let b = rho g AH for one density rho. Let B = Rho g Ah for another density Rho > rho. Compare the bouyancys b/B = rho g A H/Rho g A h = rho H/Rho h = 1 because we assume the same weight for the wood so W = b = B in this think experiment. Then we have h = (rho/Rho) H < H because rho/Rho < 1. Thus, h < H and the depth the wood sinks into a higher density water (h) is less than H for the lower density water. Which, ta da, is why you and that wood tend to float better in salt water than in fresh water.

Answer 3

Wood has a lower density than water.

Answer 4

This is what Archimedese shouted "Eureka" once he figured this out. Every object occupies certain space, it is called volume. If the same volume of water weighs more, the object is lighter than water and will float. If the volume of water weighs less, the object will sink.

Answer 5

Anything that floats has a lower density than the liquid it's floating in, anything that sinks has a higher density.

Answer 6

It has a density less than water(1 gr/cm^3).

Answer 7

Wood cells have air trapped in them.Not all wood floats.

Answer 8

It has a lower density than water.

Answer 9

it has less density then water or liquides

Answer 10

bcoz it is lighter than the same volume of water