Fundamental And Derived Quantities With Examples [Explained]
This article will explicitly explain fundamental and derived quantities in physics and their examples. Most of the examination you will likely write in physics will ask questions on this very aspect.
Measurement is a very important aspect of physics and other sciences. No fact in science is accepted, no law is established, unless it can be exactly measured and quantified. As physics is based on exact measurements, every such measurement requires two things; first a number or quantity, and secondly a unit. So at the end of this write up you should be able to distinguish between fundamental and derived quantities and units.
Read: Scalar and Vector quantities
What is a fundamental quantity?
Fundamental quantities are the basic quantities that are independent of others and cannot be defined in terms of other quantities or derived from them. They are basic quantities upon which most (though not all) quantities depend.
Fundamental units are the basic units upon which other units depend. They are the units of the fundamental quantities.
The three most important basic quantities in physics are length, mass, and time.
- Length may be defined as the extent of space or distance extended
- Mass is commonly defined as the quantity of matter or material substance.
- Time is defined as that in which events are distinguishable with reference to before or after.
Therefore, Length, Mass, and Time are the three of the most fundamental quantities.
Examples of Fundamental Quantities
There are seven (7) basic fundamental quantities in physics and they are given in the table below
| Quantity | Unit | Unit abbreviation |
| Length | metre | m |
| Time | second | s |
| Mass | kilogram | kg |
| Electric Current | ampere | A |
| Temperature | kelvin | K |
| Amount of Substance | mole | Mol. |
| Luminous Intensity | Candella | Cd |
The units in the table are in SI (Systeme International) units and are the principal system of units used in scientific work today.
Read: Questions on measurements
What is Derived Quantities?
Derived quantities and units are those obtained by some simple combination of the fundamental quantities and units. They are thus dependent on the fundamental quantities and units.
Examples of Derived Quantities
| Derived quantity | Derivation | Derived unit |
| Area | length x length | m2 |
| volume | Length x length x height | m3 |
| density | Mass/volume | kgm-3 |
| velocity | Displacement/time | ms-1 |
| acceleration | Change in velocity/time | ms-2 |
| force | Mass x acceleration | Kgms-2 (Newton, N) |
| Energy or work | Force x distance | Kgm2s-2 or Nm (Joule, J) |
| power | Work/time | Js-1 (or watt, W) |
| momentum | Mass x velocity | Kgms-1; Ns |
| pressure | Force/area | Nm-2 (pascal, Pa) |
| frequency | Number of oscillations/time | s-1 (hertz, Hz) |
