Question

Why does a ship made of iron and steel float in water whereas a small piece of iron sinks in it ?

Answer 1

Relative density is the factor on which decides whether the object will sink or float when immersed in any particular liquid. Relative density is the ratio of the density of a substance to the density of any given reference material or substance.

Complete answer:
If a substance has a relative density less than 1 then it is less than the reference and if it is greater than 1 then it is denser than the given reference substance. Here the reference substance is water and the density of water is$1\,Kg{m^{ - 3}}$. So the density of a ship or any material which should float on the water must have a density less than $1\,Kg{m^{ - 3}}$ in order to get the relative density less than 1. Relative density is given baas:
$\text{Relative density} = \dfrac{\text{Density of substance}}{\text{Density of the reference}}$

The ships are designed in such a way that it contains lots of air in it and hence the density of the whole ship becomes less than that of the density of the water hence it floats. Whereas small pieces of iron have a density much greater than the density of water, it also does not contain air to drop its density so it gets sunk easily. Hence, a ship made of iron and steel floats in water whereas a small piece of iron sinks in it.

Note: The ships and cruise are designed keeping in mind the amount of weight will be loaded on that ship, as the load will affect the average density of the ship. Heavier load could result in the sinking of the ship. The relative density of ice to water is 1 so the ice floats right on the surface of the water, and is considered as neither submerged nor floated.