how does a iron ship float?

Answer 1

Ask Archimedes.

OK take an object, any object. Ask two questions:
(1) how heavy is it?
(2) how much space does it take up?

Now figure out how much water would take up the same space that your object would take up. How heavy is that water? is it heavier than your object? then your object floats. No? then it sinks.

So your iron ship is just a big box full of air. Sure, it's heavy, but it's nowhere near as heavy as a bunch of water that takes up the same space. Water, by the way, is more or less the heaviest liquid we have available in normal conditions, apart from mercury.

What actually made Archimedes run into the street naked was the realisation that your object will sink down UNTIL it has shoved out of the way an amount of water that is exactly as heavy as it is. That's why when you load a ship up with containers/coal/passengers, it sits lower in the water than when it's empty.

Answer 2

It's all to do with the mass (weight) of the ship.

Before something can sink in water it has to have so much weight that it's able to push the water out of the way.

Water weights one ton per cubic metre so if an object is placed in water that weighs less than one ton per cubic metre it will float, if it weighs more than one ton per cubic metre it will sink.

The ship may be made of iron but it's not a solid lump of iron and so the overall weight of the ship is less than one ton per cubic metre. Iron itself will sink because it's very heavy but the ship is hollow and has a lot of air in it.

As people and cargo board the ship the overall weight increases and the ship will sit a little lower in the water. If more and more people and cargo board the ship there would eventually come a point when the ship would sink.

Let's imagine that the ship weighs 1000 tons, when placed in the water it will displace (push aside) 1000 tons / 1000 cubic meters of water - this is what's known as displacement and is a standard way of 'weighing' a ship.

Now lets imaging that the people and cargo that are loaded onto the ship weigh 200 tons. By loading them on board another 200 tons / 200 cubic metres of water will be displaced.

Now, let's assume that the ship has a volume of 2000 cubic metres. When it's empty and placed in the water it will displace 1000 cubic metres of water (because it weights 1000 tons). At this point 1000 cubic metres of the ship will be below the water and 1000 cubic metres will be above it.

As the ship is loaded with 200 tons of cargo and people it displaces 200 cubic metres more water and now has a total weight of 1200 tons. There will now be 1200 cubic metres of the ship below the water and 800 cubic metres above the water.

This is in simple terms and there's a bit more to it - eg the density of sea water isn't the same as pure water, but in essence this is how it works.

Answer 3

In the same manner that a pie pan will float in your kitchen sink. The iron ship is actually less dense than the water it displaces. If the hull is breached, and large volumes of water enter, the physics of the ship have changed, and it will not float.

Answer 4

The hollowness of the ship means that the effective density of the ship as a whole is less than water, and so the boat floats.

Answer 5

A ship is less dense than water. In other words, x cubic metres of the ship weighs less that the same x cubic metres of water.

When something is less dense than the matter around it, it floats. This is also why hot air balloons float (hot air is less dense than cool air), icebergs float (ice is less dense than water) and submarines don't just sink to the seabed (again, the submarine is less dense than water - it uses ballasts that fill up with water to adjust its overall density to control the depth at which it floats). Conversely, it's also why rocks sink in water (rocks are denser than water).

Answer 6

Because the volume of air contained within the ship is less dense than the water surrounding it. Therefore its lighter than the water..

Answer 7

It has bulk heads full of air, plus although it is iron, the weight is spread evenly, and cause it so big, it might as well be tin foil from a large scale

Answer 8

Heh! Archimedes had the answer you know. He jumped out of the bath and ran down the street naked yelling 'Eureka' apparently - or something like that! All to do with 'displacement.'

Answer 9

Displacement... a little principle, but it keeps those heavy ships afloat.

Answer 10

Oh sweetie, if you don't know. why did you waste your time writing it (I know - 2 points) and more importantly, OUR time having to read it until we get to a proper answer or two