# Appendix B

# Units in Physics

## B.1. Multiples and submultiples of units

The multiples of units and their submultiples by powers of 10 are designated as in Table B.1.

**Table B.1.** *Multiples and submultiples*

## B.2. Fundamental and derived SI units

The units of all physical quantities are defined in terms of six *fundamental* (or *basic*) *units*, which are chosen by convention: *length*, *time*, *mass*, *current intensity*, *temperature*, and *luminous intensity*. The units of the other physical quantities (the so-called *derived units*) are defined in terms of the fundamental units by using the dimensional homogeneity of physical laws. The International System of Units (SI) used in the book has the *meter* (m), *second* (s), *kilogram* (kg), *ampere* (A), *kelvin* (K), and *candela* (cd) as fundamental units. However, some branches of science and engineering continue to use the CGS system (based on the *centimeter*, *gram*, and *second*) for mechanical quantities. As the whole circumference is divided into 2π *radians*, the unit of angles is the radian. We also use the degree (°), *minute* (′), and *second* (″), and sometimes *revolution* (2π radians).

## B.3. Mechanical units

**Table B.2.** *Mechanical units*

## B.4. SI electromagnetic units