How Do Ocean Liners Float?

The average density of an ocean liner allows it to float.

Ocean liners, which include large ships such as cargo ships and cruise vessels, are often made of steel and are quite heavy. It often looks and seems impossible that something that weighs so much is able to float on the water, but there is a scientific explanation.

Function

An ocean liner takes advantage of its average density, the density of both the steel frame and all the air filling the empty spaces, to float on the water. The steel's density is greater than the water, but the empty spaces full of trapped air weigh less and help the liner stay afloat. While gravity is pushing the liner down into the water, the buoyant force, or the pressure from the ocean, is pushing it up at the same time.

Effects

Ocean liners with a greater average density, such as a cargo ship full of boxes, sit lower in the water than empty cargo ships because there is more pressure pushing down onto the water. If too much cargo is placed in an ocean liner and not enough air is trapped to help lower the average density, the ship will sink.

History

Archimede's Principle is a concept relating to buoyancy that helps explain how objects are able to float. It was discovered when Archimedes, a Greek mathematician, noticed that when objects entered the water, the level of the water rose. He theorized that the water the object displaced was equal in weight to the buoyant force from the water.

References

• Science With Me: Science for Kids: What Floats Your Boat?
• Boat Safe Kids: How Does a Heavy Boat Float?