## 2007-09-19

### Understanding Derived and Base Quantities

Understanding Derived and Base Quantities

Physical quantities are quantities that can be measured. e.g. Length, Temperature, Speed, Time.

Quantities or qualities that cannot be measured are not physical quantities. e.g. happiness, sadness etc.

Physical quantities can be divided into Base quantitied and Derived quantities.

(i) Physical quantities are quantities that can be measured or can be calculated.
(ii) The base quantities are “building block” quantities from which other quantities are derived from.
(iii) The base quantities and their S.I. units are:

• Base quantities S.I. units
• Mass kg
• Length m
• Time s
• Electric current A
• Thermodynamic
• temperature K

(iii) Derived quantities are quantities derived (iv) Examples of derived quantities.

• Derived quantities S.I. units
• area m2
• density kg m-3
• weight N
• velocity m s-1

Standard Notation: To express very large or very small numbers.
Example; A X 10 n (ten to the power of n), n must be an integer and 1 ≤ A