This article explains how objects float and sink in water, and specifically how submarines use buoyancy tanks to control their depth in the water. It covers how buoyancy principles in the natural world are related to how submarines function.
If you put a rubber duck in the water in a bathtub, it will quickly float back up. However, if you put your body in the water of a bathtub, it will sink to the bottom of the tub. Similarly, objects either float to the surface or sink to the bottom when they enter water. However, there is an object that can sink to the bottom of the water and rise to the surface again, depending on the circumstances. This is a submarine. Submarines can control how deep they go underwater without using the power of their engines. How does a submarine control its depth?
First, let’s understand the difference between objects that float and objects that sink. To understand how submarines work, we need to take a quick look at their history. The first submarine is believed to have been built by Dutch inventor Cornelius Drevel in the 17th century. His submarine was simply a small wooden vessel that moved through the water using human power, but over the next few centuries, submarines evolved for military purposes and became more complex. At the core of this development was an understanding of buoyancy and gravity.
Gravity acts equally on objects submerged in water. However, an object floating on the surface of the water is at rest, which means that the total magnitude of the force acting on it is zero. This is because there is another force acting in the opposite direction of gravity: buoyancy. First discovered by the ancient Greek scientist Archimedes, buoyancy is the reaction of an immersed object to the push of water. Its magnitude is equal to the weight of the water it pushes away, and the amount of water it pushes away is equal to the volume it occupies in the water. In other words, an object floating on water pushes out as much water as it weighs, so that gravity and buoyancy are in equilibrium.
An object that sinks into the water sinks because it weighs more than its volume of water. So you can see that whether an object floats or sinks in water is determined by its mass per unit volume, or density, which is whether it is less or more than the density of the water. Submarines use this property to maneuver through the water by controlling their density.
So how do submarines manage to control their density underwater? Buoyancy tanks are used to control the density of the submarine. A buoyancy tank is a structure on a submarine that consists of large hollow spaces that can be filled with air or water. When the submarine goes underwater, the buoyancy tank is filled with seawater to increase its density. When the submarine comes to the surface, the external valve of the buoyancy tank is opened while blowing compressed air into the buoyancy tank. This allows the seawater in the buoyancy tank to drain to the outside and the inside of the buoyancy tank to fill with air, reducing the overall mass of the submarine. However, the volume that the submarine occupies in the water remains the same, so the density of the submarine also decreases. This makes the average density of the submarine less than the density of seawater, and the submarine is able to float to the surface.
The buoyancy tanks also serve to keep the submarine’s weight and buoyancy equal so that it can travel at a certain depth underwater. At this point, the density of the submarine matches the density of the seawater, and the buoyancy is called neutral buoyancy. Neutral buoyancy allows the submarine to maintain its depth and conserve fuel, making it efficient for long dives.
The principle of these submarines is the same as that of a fish’s boule. Submarines use the same principle as fish to regulate their depth in the water by controlling gravity and buoyancy in the water.
This feature of submarines is important not only for military purposes, but also for scientific exploration. Ocean researchers use submarines to explore deep-sea environments, investigate undersea resources, and help protect marine ecosystems. This is helping humanity gain a deeper understanding of the Earth and its oceans.
