Introduction

The International System of Units1 is the world’s most widely used system of measurement. The International Organization for Standardization (ISO) laid it out in ISO 31 and ISO 1000. The modern SI system will be used through out this textbook. Common quantities, their variations, as well as conversion tables may be found in [11]. The most important physical quantities, their

and

are in Table 1.1. The unit rad can be replaced by the numeral 1 in calculations.