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Why does a piece of wood sinks in water but not boat made of it?

Example-when we throw a small piece of wood in river,it sinks but boat doesn't......

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Wood will often float until it becomes water logged. But back to your question...for the same reason a huge aircraft carrier or cruise ship made out of metal doesn't sink. Displacement or Archimedes' Principle, the law that a body immersed in a fluid is buoyed up by a force (buoyant force) equal to the weight of the fluid displaced by the body.

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Outstanding answer!
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Finally, this makes sense.
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It's the SHAPE of the boat that keeps it afloat ... Hey that rhymed! Look at an aircraft carrier! That's made of STEEL! How does THAT float? ... The shape.

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Just like the motion of the ocean
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It's science? Awww, I thought it was magic. Thanks for taking the fun out of it. :(
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Don't know if they still do this but every spring at Iowa state they had the engineering student build boats out if cement and sailed them in a lake on campus.
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Jamie Hyneman and Adam Savage made a boat of frozen wet newspaper and sailed it around til it thawed out and began to disintegrate.
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Well, wood is lighter/less dense then water, and boats are designed to be water tight, allowing it to displace water and not let any in, not if water breached the hull, then it would sink. But almost all types of wood are lighter than water.

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Because of the air trapped inside of the wood. It creates buoyancy. Look at an ocean vessel. They are made of steel.

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It shouldn't sink when you throw it in the river. Wood usually floats. But anyway, boats don't sink, even steel-hulled boats, because of weight displacement. The way they are shaped they are lighter than the volume of water they displace, so they float on top. If the hull springs a leak the vessel fills with water which pushes out the air. This adds a lot of weight which changes the weight displacement. The ship filled with water becomes heavier than the water itself and it sinks to the bottom.

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Brilliant answer, as always.
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Whether or not a ship floats or sinks, is determined by the boat and the amount of water it displaces

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My Bass Tracker doesn't sink !
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Well that's good, because I hear you go fishing where alligators swim. hehe :)
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Yep , got a good picture of it !
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DISPLACEMENT. If the object weighs more than the water it displaces, then it will sink.

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cindysonthenet

The boat forces more water than its weight because of its size and shape then a log does; most of the inside of a boat is air, which is very light. This explains why massive ocean liners float: as long as the water displaced weighs more than the ships themselves, they will not sink.(what is buoyancy)

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