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  • Writer's pictureSiheli Siyathra

Why Does a Steel Ship Float?

All sorts of objects can float, regardless of their shapes or sizes. Whether an object is flat, pointy, hollow, or solid does not affect its ability to float. When an object enters water, it pushes out a volume of water equal to its own volume to make space. This is called displacement.

Two forces act on an object when it enters water: a downward force called gravity and an upward force called buoyancy. An object’s weight measures the downward force of gravity. If the object displaces an amount of water equal to its volume, the buoyant force and gravity will be equal. Then, the object will float. But if an object weighs more than the water it displaces, the buoyant force will be less than gravity. Then the object will sink.

Any object in water has some amount of buoyancy and gravity acting on it. This means that any object in water loses some weight. How compact an object is, determines whether it will float or sink. This compactness is referred to as density. Density can be defined as mass per unit volume. If an object is denser than water, it will sink. A piece of steel is denser than water. If so, why does a ship float?

A ship floats when it can displace water equal to its own weight. What’s more, a steel ship is not made of solid steel. It’s hollow and contains a lot of air. Air is a much less dense substance than water.

Calculating the density of a steel ship with the formula “density equals mass over volume” should show that the ship is less dense than water. The buoyant force pushing up on the ship is equal to the gravity pulling the ship down. This is why a steel ship floats.

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