Definition of a Fundamental Quantity
A fundamental quantity is a physical quantity that is considered basic and independent, meaning it cannot be expressed or defined in terms of any other physical quantities. These quantities serve as the foundational building blocks for all other measurements and calculations in science.
The Seven SI Fundamental Quantities
The International System of Units (SI) defines seven fundamental quantities: length (measured in meters), mass (kilograms), time (seconds), electric current (amperes), thermodynamic temperature (kelvin), amount of substance (moles), and luminous intensity (candelas). Each has a specific, globally accepted standard for its measurement.
Distinction from Derived Quantities
Fundamental quantities stand in contrast to derived quantities, which are defined and expressed as combinations of fundamental quantities. For example, speed is a derived quantity, calculated by dividing distance (a fundamental quantity of length) by time (a fundamental quantity of time). Force, volume, and density are other common derived quantities.
Importance in Science and Engineering
These foundational quantities are crucial because they establish a universal and consistent framework for describing the physical world. By agreeing on these basic, independent quantities, scientists and engineers worldwide can accurately communicate, compare, and reproduce experimental results, ensuring the integrity and progress of scientific knowledge.