# how is it possible for a ship that weighs thousands of tons to 'float' on water?

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• Anonymous

The simple answer is that ships, even those weighing hundreds of thousands of tons, weigh less than water. More-precisely, they weigh less than the amount of water they displace. To understand this better, let's do a mental experiment...

Imagine a ship floating in water. Now imagine that the water turns into Jello and we remove the ship. That will leave us with a hole in the Jello of the exact size and shape of that part of the ship that was below the water. Finally, we fill the hole in the Jello with water. The weight of that water will be exactly equal to the weight of the entire ship. That's why the ship will float. This is because any floating body will displace an amount of liquid equal to its weight. As long as the weight of the displaced water is greater than the weight of the object, the object will float. If the weight of the water is less than the object, the object will sink.

When engineers design ships they need to predict ahead of time that the ship's density is less then the density of water

Density of an object is:

The weight of an object divided by the volume of an object.

When someone describes how dense something is they may say it is 0.285 lbs for every cubic inch...

Yes, a solid steel bar would sink in water. BUT, an empty shell of steel (expecially the very large size of a ship) is NOT very dense at all. It's density is much closer to the density of air which is not very dense.

For example:

- Water weighs 62.43 lbs for every cubic foot

- A solid cube of steel (1 foot cube) weighs 492 lbs... it will sink as its weight is more than 62.43 lbs

- That same cube of steel, but hollowed out with an air pocket with a really thin wall would weigh about 12 lbs. It will float as it weighs much less than 62.43 lbs

Also check into what is called specific gravity

• 006
Lv 6

The ship as a whole (which includes the air inside it) is less dense than the water, so it floats. It's the same thing that keeps a hot-air balloon above the ground, even though the balloon itself weighs hundreds of pounds.

When the air inside a boat is replaced with water (like the Titanic), it sinks.

• Anonymous

The same way fog banks that weigh billions

of tons float on water. Displacement.

All your answers are correct but the weight of a ship is calculated from the weight of the water it dispaces when first floated (empty) so a 200,000 ton tanker does not weigh anywhere near that

• Anonymous

In order for something to "float" on water, the amount of water that is displaced "replaced" by the object, must be equal to or greater than the mass of the object itself.

Thus the huge surface areas. Think of it like this, why is it that when you go vertically into water, you sink till about your chest, but when you go in horizontally you float, its the surface area over your entire body displacing the large amount of water.

The earth has the gravity to make the water repel the ship and water at the same time gravity uses a different force for example tides and other natural formats that come into effect naturally in the life of our planet earth

Upward water pressure pushing on the bottom of a steel boat causes the boat to float. Each square inch (or square centimeter) of the boat that's underwater has water pressure pushing it upward, and this combined pressure floats the boat.