What is the difference between density and relative density?

1 Answer
May 23, 2016

Answer:

Please see below.

Explanation:

The density is mass divided by volume and hence it has a unit - say in SI units it is #(kg)/m^3# and in FPS units it is #(lb)/(ft)^3#.

For example density of water in SI units is #1000(kg)/m^3# and in FPS unit it is #62.42796(lb)/(ft^3#.

For iron it is #7874(kg)/m^3# or #491.55776(lb)/(ft^3#.

Relative density on the contrary is the ratio of the density of certain matter with that of water. Hence, it does not have a unit, but is just a number. As such, it's value will not change when we change units, as both densities are calculated as ratio.

It is obvious that for water it is just #1# and for iron it will always be #7.874# , whatever units one uses.