Question

When, why an iron needle sinks in water, but a ship made of iron floats on water.

Answer 1

Hint: Iron needle easily sinks in water whereas an iron ship floats on water because water has density depending on the density of water only iron needle sinks and a ship made of iron floats on water. It’s because of density, let's discuss this relation clearly.

Complete answer:
Let's discuss needle sinks in water, as the weight of water displaced by an iron needle is less than the weight of a needle. Density of iron is more than the density of water, so the iron needle sinks in water. Needles displace more water than its weight. The weight of the needle is less than the weight of fluid displaced by the body. Specific gravity of the needle is greater than water displaced by it. Displacement of the needle is less than the displacement of water.

Now we are discussing, an iron ship floats in water, because a ship is made of iron and steel, it has a lot of space filled with air. This causes the ship displaced in water is equal to the weight of the ship. Ship is hollow and empty space contains air, makes the average density of water is less than the average density of water and it floats on water.

Incase of larger ships, the weight of water displaced by the ship is higher than the weight of the ship. When a ship enters into the water it will displace a large amount of volume. Whereas, the displacement of a ship made of iron and steel is greater than the displacement of water.

Note: In floating, the body will experience some no net downward force. To float on water the weight of the body is greater than the actual weight of the body. Water has density and that density is less than the object then it sinks in the water, whereas the density is higher than the object then it floats on the water.