# The Naked Scientists Forum

### Author Topic: 5 gram coin sinks. 10 TON battleship floats? wtf?  (Read 6561 times)

#### Ben6789

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« on: 17/04/2007 13:18:15 »
I don't understand this at all..I thought lighter things floated on water. I find this fact weird. How does it work?

#### Seany

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #1 on: 17/04/2007 15:36:01 »
Erm.. I bet someone else has a better explanation to this. But I will try.

A boat, has sides which go up towards the sky, so that water cannot enter the boat. Unlike a coin, which do not have sides which are curved, the boat does. If you just place a coin, the water will rush over the coin creating it to sink.

With a boat. This is different.

The boat will manage to retain the water from entering, unlike the coin. As long as the water does not go over the water, it will pretty much float. The reason in this is because the oxygen on the boat, is lighter than water, so it floats.

If we lie on water, and take in lots of oxygen, we will float. If we lie on water, and breathe out as much oxygen as possible, we will start sinking.

In this way, if the boat has oxygen, then it will float.

I think that there is another reason why, but this is one too.

#### science_guy

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #2 on: 17/04/2007 15:46:22 »
That is entirely correct.

A battleship may be 10 tons, but when you take it's total area, and divide it by it's total mass, then you get a density less than the coin, that, along with the curved sides, is what floats your boat.

edit: originally put mass/mass=density as opposed to area/mass=density
« Last Edit: 17/04/2007 15:51:06 by science_guy »

#### Seany

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #3 on: 17/04/2007 15:47:28 »
Thanks ^^

#### Ben6789

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #4 on: 17/04/2007 16:11:37 »
thanks guys!

#### Mirage

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #5 on: 17/04/2007 17:57:10 »
Certainly is amazing with heavy metal ships floating, the same amazement that we have these huge heavy planes in the sky

#### Paul123

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #6 on: 17/04/2007 18:20:21 »
That is entirely correct.

A battleship may be 10 tons, but when you take it's total area, and divide it by it's total mass, then you get a density less than the coin, that, along with the curved sides, is what floats your boat.

edit: originally put mass/mass=density as opposed to area/mass=density

You mean mass/area=density.

#### eric l

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #7 on: 17/04/2007 19:08:38 »
That is entirely correct.

A battleship may be 10 tons, but when you take it's total area, and divide it by it's total mass, then you get a density less than the coin, that, along with the curved sides, is what floats your boat.

edit: originally put mass/mass=density as opposed to area/mass=density

You mean mass/area=density.

Would that not be  :  mass / volume ?

Allthough area will play a role :  e.g. you can make a Gilette-type razor blade float if you manage to put it flat on the surface of the water.

#### Bored chemist

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##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #8 on: 17/04/2007 19:31:39 »
Floating razor blades are to do with surface tension. Interesting enough, but not what we are on about here because it's not strong enough to hold coins or ships. Also, needles float pretty well too and they have a lot less area than a razor blade.
What keeps the boat up is nothing much to do with its area.
You could make a boat with a very deeply corrugated hull that had lots of area and it would still float.
What holds the boat up is the upthrust. This is equal to the weight of the water displaced (ie to the product of the density and the volume). (Can anyone here spell Archimedes?)
The ship floats because most of it is air and overall it weighs less than the same volume of water.
« Last Edit: 17/04/2007 19:33:51 by Bored chemist »

#### Paul123

• Jr. Member
• Posts: 20
##### 5 gram coin sinks. 10 TON battleship floats? wtf?
« Reply #9 on: 18/04/2007 20:57:03 »
That is entirely correct.

A battleship may be 10 tons, but when you take it's total area, and divide it by it's total mass, then you get a density less than the coin, that, along with the curved sides, is what floats your boat.

edit: originally put mass/mass=density as opposed to area/mass=density

You mean mass/area=density.

Would that not be  :  mass / volume ?

Allthough area will play a role :  e.g. you can make a Gilette-type razor blade float if you manage to put it flat on the surface of the water.