Question

Why do you have different units for the same physical quantity

Answer 1

Different physical quantities have different units to avoid inconvenience. For example the S.I unit of length is meter (m). But while measuring the lenght of a pencil, we could use the smaller unit of length, cm. If there was only one unit of length for instance meter... then the measurement of a 6 cm pencil would have been used as 0.06 m....which is inconvenient. however when we measure the distance b/w two cities we measure it with kilometer (km). If we would measured it in cm,then the magnitude will be very long.

hope it helps...