How is it that ships made largely of steel can float when the density of steel is much higher than the density of water? Why is it possible to make oil tankers much larger than other ships (and what happens when an oil tanker is unloaded?)
The steel hull encloses a volume that displaces an amount of water with much more mass than the steel's.
The air in the volume weighs much less than the water it displaces, so the net effect is to make the whole shebang float.
Ships made of steel can float because of a principle known as buoyancy. Buoyancy is the force exerted by a liquid, such as water, that opposes the weight of an immersed object. Although the density of steel is indeed higher than that of water, the overall shape and design of the ship allow it to displace a volume of water greater than its own weight.
To understand this concept, let's explore a bit of physics. The buoyant force acting on an object immersed in a fluid is equal to the weight of the fluid the object displaces. In other words, the weight of the water "pushes back" on the ship, creating an upward force that helps to counteract the ship's weight.
Ships are designed with a hollow structure called a hull, which contains air-filled compartments. These compartments, known as ballast tanks, contribute to the ship's buoyancy. By adjusting the amount of air or water in the ballast tanks, the ship's overall density can be controlled, allowing it to float steadily. Additionally, the shape of the hull is designed to displace a large volume of water, further enhancing its buoyant force.
Now, let's discuss the size of oil tankers compared to other ships. Oil tankers can be much larger because they transport liquids with lower density, such as oil, which makes them inherently more buoyant. Oil is less dense than water, so even though the tanker itself is massive, it can still float due to the principle of buoyancy.
When an oil tanker is unloaded, oil is pumped out of the tanks, which significantly reduces the weight of the vessel. As the weight decreases, the buoyant force increases, lifting the tanker higher in the water. This unloading process allows the tanker to maintain stability and balance while keeping a safe distance between its hull and the waterline.
In conclusion, ships can float due to the principle of buoyancy, where the weight of the water displaced by the ship is greater than its own weight. The design and shape of the ship, along with hollow chambers and ballast tanks, contribute to its buoyancy. Oil tankers can be larger because the oil they transport has a lower density than water. When an oil tanker is unloaded, the weight decreases, increasing the buoyant force and lifting the ship higher in the water.