The two types of physical quantities are elemental quantities and derived quantities.
Understanding Physical Quantities
Physical quantities are measurable properties of a system or phenomenon. They describe the physical world quantitatively. It’s important to understand how these quantities are categorized to properly analyze and interpret physical phenomena. The classification into elemental and derived quantities helps simplify this understanding.
Elemental Quantities
Elemental quantities, also sometimes referred to as base quantities, are the fundamental building blocks of all physical measurements. These quantities are defined independently and are not expressed in terms of other quantities. The reference indicates seven such fundamental quantities:
- Mass: A measure of the amount of matter in an object.
- Time: A measure of the duration between events.
- Temperature: A measure of the average kinetic energy of particles within an object.
- Mole: A measure of the amount of a substance.
- Length: A measure of spatial extent.
- Luminosity: A measure of the intensity of light emitted.
- Electrical charge: A measure of a fundamental property of matter causing it to experience a force in an electromagnetic field.
Derived Quantities
Derived quantities are physical quantities that are defined by combining elemental quantities through multiplication, division, or other mathematical operations. They depend on elemental quantities for their definition. Derived quantities include:
- Speed: Calculated as distance (length) divided by time.
- Area: Calculated as length multiplied by length.
- Volume: Calculated as length multiplied by length multiplied by length.
- Force: Calculated as mass multiplied by acceleration (which is length divided by time squared).
- Energy: Often derived by combinations of force and length and others.
Summary
The difference between elemental and derived quantities lies in their independence. Elemental quantities are fundamental and defined on their own, whereas derived quantities are built from elemental ones. It is through these combinations that we are able to describe the complexities of the universe.
| Quantity Type | Definition | Examples |
|---|---|---|
| Elemental Quantities | Fundamental quantities not derived from other quantities | Mass, time, temperature, mole, length, luminosity, electric charge |
| Derived Quantities | Quantities derived using elemental quantities | Speed, area, volume, force, energy |
