It may surprise you that cargo ships weighing tons can survive despite the addition of tons of cargo. Or, if you do not have a good grasp of certain physics concepts, you may accept it without knowing the background. Of course, there is no rule that says “everyone will be an expert in everything”.
However, we try to explain such confusing situations to you in their simplest form. We have prepared an enlightening article about the fact that parrots can speak, although monkeys, which were previously seen as closer to humans, cannot speak. Now we’re talking about how ships can stay afloat.
When you throw a tiny nail into the water, it sinks, how can huge ships stay afloat? We actually found the answer thousands of years ago:
- Patchy Fish
Let’s briefly tell the story of this. King of Ancient Greece II. Hiero asked the famous mathematician and physicist Archimedes to build a huge ship. Known as the Titanic of antiquity, this ship was named the same as the Italian city of Syracuse, which was then included in the empire.
The ship in question was intended to be so large that there would be enough space for a bath with hot water, a library, and large sculptures. As if this were not enough, the ship in question would have the capacity to carry cargo. We’re not talking about a few animals or hundreds of pounds of material here.
It was desired that tons of materials could be transported by ship:
400 tons of grain, 74 tons of drinking water, 600 tons of silk and many other materials of this size would be transported on this ship. There would also be a large number of passengers, soldiers and even horses.
Even if you were a prominent scholar of the time, upsetting the king would be the last thing you would want to do:
Being aware of this, Archimedes started to think about how to float a ship of this size and capacity. While thinking about it, it is thought that he is in a bath, in a bath. It is thought that our scholar, who saw that he felt lighter when he entered the water and that the water level rose, got excited later and the events were connected to the famous Evreka story at this point.
If you don’t know that story, we briefly told it here. Although the place they are connected to is the same, the debates of historians continue:
It is thought that this confusion may have arisen by mixing Korōnē, meaning keel of a ship, in Greek, and Corona, meaning crown.
Now let’s get back to our ship. How is this big thing going to swim?
What Archimedes found was exactly this: “An object immersed in water exerts a buoyant force equal to the weight of the water displaced by the object.” In other words, if the weight of the object you put in the water is less than the weight of the water it displaces, the water will easily lift the object.
If you have a 5-pound object in your hand, and that object displaces (or displaces) exactly the equivalent of 5 kilograms of water, it will be at the glide point:
But if you make a 5 kg object displace the equivalent of 7 kg of water, the water will exert a 7 kg buoyant force on a 5 kg object. In this context, the object floats freely. However, if your 5 kg object only takes up an amount of water equivalent to 3 kg, the force exerted by the water is not enough to carry this object and therefore the object will sink.
Here we use density. If you divide the mass of an object by its volume, you will find its density. Let’s move forward with examples of nails and ships:
There are no gaps in the nails. They are made entirely of steel. In order for them to float when you drop them into the water, the gravity, which increases in proportion to their weight, must not get in the way of the buoyant force. But the buoyant force exerted on a nail is less than its own weight. Therefore, gravity (or weight) prevails and the nail sinks.
If we didn’t leave any space inside the ships and they were just huge piles of metal, they would suffer the same fate as nails:
But ships have air gaps. Thanks to their very large volume, they replace a large amount of water, but thanks to these air spaces, their weight does not exceed the weight of the amount of water they are replacing. When ships have an accident, they sink because they get heavier when water fills these gaps.
In other words, if a 1500-ton ship were to replace 1000 tons of water, a buoyant force of 1000 tons would be applied to it. But despite this, the ship would sink as the weight of the ship would remain 500 tons. For this reason, ships are designed by paying attention to this principle of Archimedes.
It is possible for ships to carry more cargo by displacing more water:
For this reason, we can say that they are sunk more. Mandatory markings on cargo ships, known as the Plimsoll line, indicate how far the ship can be sunk during cargo loading. Roughly speaking, sinking more means displacing more water and facing more buoyancy. However, this sign is used because different types of water have different buoyancy. If these safety lines are exceeded, the ship is in danger of sinking.
Since this is of vital importance, it is present on every cargo ship as a safety precaution today. Different letters and lines on it show how much cargo can be taken in different seasons and types of water (sweet, tropical, salty).
Sources: Casual Navigation, Sabins, Dr. Hany Farid, TedEd, Marine Education Portal, Syracusia
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