Question

Why does the same physical quantity have various units?

Answer 1

Physical quantities:

1. For the same physical quantity, we use many units. For example, Joule is the unit of energy in the SI system, but erg is the unit of energy in the CGS system.
2. There are many different types of mass, matter, energy, etc. in this cosmos. These physical quantities have a very wide range.
3. The key justification is that we developed several units to make computations simpler because a quantity can fluctuate over a wide range. Therefore, several units are employed for the same physical quantity in order to facilitate measurement and simplify calculations.

Some examples are provided below:

$$\begin{gathered} 1\mathrm{Tone}=1000\mathrm{kg} \\ 1\mathrm{Slug}=14.6\mathrm{kg} \\ 1\mathrm{Pound}=0.45\mathrm{kg} \end{gathered}$$

A $\mathrm{kilogram}$ is the S.I unit of the mass.