All these quantities are derived quantities, and they need more than one basic physical quantity to define their units. Sometimes a name of a scientist who discovered this phenomenon is used as the name of the unit as in the case of the units of the force as Newton for the purpose of simplicity. Newton is defined as kilograms meters per second square . It is clear from the above that all physical quantities need to identify by a unit. These three examples illustrate the need to have a uniform and standard of measurement units as illustrated in Table .