Physical Quantities and Units
Read this text to review these physical quantities and units. Make sure you are familiar with the prefixes, symbols, values, and examples in Table 1.2. We will use them frequently during this course.
SI Units: Fundamental and Derived Units
Table 1.1 gives the fundamental SI units that are used throughout this textbook. This text uses non-SI units in a few applications where they are in very common use, such as the measurement of blood pressure in millimeters of mercury (mm Hg). Whenever non-SI units are discussed, they will be tied to SI units through conversions.
| Length | Mass | Time | Electric Current |
|---|---|---|---|
| meter (m) | kilogram (kg) | second (s) | ampere (A) |
Table 1.1 Fundamental SI Units
It is an intriguing fact that some physical quantities are more fundamental than others and that the most fundamental physical quantities can be defined only in terms of the procedure used to measure them. The units in which they are measured are thus called fundamental units. In this textbook, the fundamental physical quantities are taken to be length, mass, time, and electric current. (Note that electric current will not be introduced until much later in this text). All other physical quantities, such as force and electric charge, can be expressed as algebraic combinations of length, mass, time, and current (for example, speed is length divided by time); these units are called derived units.