Question

Why do we have different units for the same physical quantity?

Answer 1

Every country has their own measuring system. Different ways of making measurements lead to different units.

As we know foot, pound and second are used in British and meter, kilogram and second are used in India.

Mass ranges from ${10}^{-30}kg$ (for an electron) to ${10}^{-53}kg$(for the known universe). We need different units to measure them because bodies differ in order of magnitude significantly.

And also, to make measurement easier and to simplify the calculation, different units are used for same physical quantity.

Final Answer: Because bodies differ in order of magnitude significantly.