In learning physics we need to carry out investigations. we gather information through observations and taking measurements. We measure many types of physical quantities. A physical quantity is a physical characteristic that can be measured. The value of the measurement consists of a numerical magnitude and unit. All physical quantities can be classified inti two groups : base quantities and derived quantities. Base quantity are quantity that cannot be defined interms of other base quantities. There are five base quantities : length, mass, time, current and temperature. Table 1.1 below shows the five base quantities and their respective SI units.
|Base Quantity||Quantity symbol||SI unit||Symbol|
A derived quantity is one which obtained by combining base quantities by multiplication, division or both these operations.
We use prefixes to simplify the expression of very big or very small numerical values of pysical quantities. Prefixes are usually used to express some physical quantities that are either very big or very small.