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The ship is made of metal but does not sink

Hi Steemian how are you? Hopefully healthy and creative work.
When passing through the harbor we saw many large ships. Various types of ships ranging from barges, large sailboats and several speedboats are at the dock.
Suddenly my child asked
"Dad, the shipbuilder's material is iron, right? But why aren't they sinking?" This certainly makes me surprised because it will be 8 years old to ask things that were unthinkable by adults because seeing the ship is a normal thing.
"Don't we wash all the metal spoons in the bucket?"
I was very happy to hear my child's critical attitude. I hope this attitude will become more physical until he grows up.
Finally, I tried to explain with understanding and memory when I was in school to answer why the ship did not sink even though it was made of iron.

Ship density is smaller than water density

Each object has a density (sometimes also called Specific Gravity). Mass density is defined as the ratio between the mass and the volume of the object. This means that the smaller the mass of the object (the lighter), and the greater the volume of the object, the smaller its density.
We also know that an object will float, float, sink in a liquid. All these conditions are greatly influenced by the density of the object compared to the density of the liquid in which it is dipped.
The object will float if the density of the object is smaller than the density of the liquid. The object will float if the density of the object and the liquid are the same. The object will sink if the density of the object is greater than the density of the liquid.
Likewise, what happened in the spoon and ship. The spoon will sink because the density of the needle is greater than the density of the water, and also still greater than the density of the ship. another question will definitely arise why the density of the ship can be smaller than the density of the needle?
The reason is that ships have such a large space and air-filled cavities, which makes the volume of ships so large and results in smaller density.
As I wrote before we must remember that density is mass divided by volume. If the volume gets bigger while the mass is fixed, then the result of the distribution would be smaller right?
The spoon has a smaller mass because there are no spaces, while the ship on the ship actually has a larger volume so that the smallest density.

The ship leaked so it sank

The size of the bear ship can still float because its density is smaller than water. But if the ship is perforated and water enters then the ship can sink. This can happen because the volume of the ship that was filled with air gradually filled with water so that it will increase the density of the ship. If this continues, the ship will sink.
My child is satisfied with the explanation I gave.
Thus my writing this time may be useful for all of us.

Thank you for reading my post. I hope you enjoy it