Ships are able to float on the surface of water despite their density being greater than that of liquid water due to a principle known as buoyancy. Buoyancy is the upward force exerted on an object submerged or floating in a fluid (in this case, water), which opposes the force of gravity.
The key concept behind buoyancy is Archimedes' principle, which states that when an object is submerged in a fluid, it experiences an upward buoyant force equal to the weight of the fluid it displaces. This buoyant force acts in the opposite direction to gravity, effectively reducing the net downward force on the object.
Ships are designed to take advantage of this principle. They are hollow structures with a large volume, which allows them to displace a significant amount of water. Although the ship's total mass may be greater than the mass of the water it displaces, the buoyant force exerted on the ship by the water is still greater than the weight of the ship itself.
When a ship is placed in water, it sinks until it displaces a volume of water equal to its own weight. At this point, the upward buoyant force is equal to the downward force of gravity, resulting in a state of equilibrium. The ship then floats, with only a portion of its hull visible above the waterline.
It's important to note that the density of the ship itself doesn't determine its ability to float. Instead, it is the relationship between the density of the ship and the density of the water it displaces that determines whether an object will float or sink. If the density of the object is less than that of the fluid it displaces, it will float. If the density is greater, it will sink.
Ships are typically constructed using materials with lower densities than water, such as steel or aluminum, which helps reduce their overall density. The shape and design of the ship also play a role in maximizing buoyancy and stability.
In summary, ships float on water due to the principle of buoyancy. Despite having a higher density than water, ships are designed to displace a volume of water greater than their own weight, resulting in an upward buoyant force that enables them to float.