Why is that an iron Rod sink in water? But imagine a ship made by an iron rod does not sink?

This question was asked by one of our readers and I considered it worthy of a blog post.

The ability of an object to float on water depends on factors such as the nature of object, the surface area and so on.
Let's consider the principle of floatation popularly known as Archimedes's principle, he noted that for an object to float on water, the weight of object must equal the upthrust on the object when immersed in water.
However it's most important to know that an object only floats on a water if and only if the weight of the body equals the upthrust before it's fully immersed in a liquid.
Have you witnessed that it's possible for a rubber cup containing water to sink in a bucket of water and a steel cup to float. The both can sink and float based on the condition stated above.

Coming back to your question, you pointed out that iron sinks and so should anything made of it. That's wrong.
Here we are talking of the surface area, ship has a large surface area and thus before it can sink, it has to displace a large amount of water and its weight on the water leads to increase in upthrust on the ship and thus the weight and the upthrust equals each other.
The effect of surface area can be seen in this way.
We know if a stone and a paper are fallen at a height and at the same time in a vacuum, they land the same time. Why that's is not true if done in the atmosphere is that the stone has small surface area unlike the paper.

So the paper has to overcome more resistance from the air i.e displace more air to land compared to the stone.

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