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List of physical quantities
From Wikipedia, the free encyclopedia
The primary dimensions of physical quantities are arbitrary and depend on the choice of units. I is usually based on the base units of the International System of Units.
Other dimensions, such as force rather than mass, or charge [Q] rather than current [I], could be used. Even the number of dimensions is not fixed. In the three-base unit cgs system, for example, the units of charge are erg½ cm½ and the dimensional analysis of this quantity in terms of base units is [M]½ [L] [T]-1, whereas in the analysis below charge has units of [I][T].
Also note that the symbols are not International Standards and may be used differently than shown here.
| Base quantity | Symbol | Description | Dimension and units (SI) | Comments |
|---|---|---|---|---|
| Length | l | The one dimensional extent of an object. | metre (m) | |
| Mass | m | The amount of matter in an object. | kilogram (kg) | extensive |
| Time | t | The duration of an event. | second (s) | |
| Current | I | Rate of flow of electrical charge. | ampere (A) | |
| Temperature | T | Average kinetic energy of particles in an object. | kelvin (K) | intensive |
| Number of particles | n | Number of particles compared to the number of atoms in 0.012 kg of 12C. | mole (mol) | extensive |
| Luminous intensity | L | Amount of energy emitted by a light source in a particular direction. | candela (cd) | |
| Derived quantity | Symbol | Description | Dimensions and units (SI) | Comments |
| Acceleration | a | Rate of change of the speed or velocity of an object. | m s-2 (metre per second squared) | scalar or vector |
| Angle | θ | Measure of a change in direction. | radian (rad) | |
| Angular acceleration | α | Rate of change in angular speed or velocity | s-2 | radian per second squared |
| Angular speed (or angular velocity) | ω or ω | The angle incremented in a plane by a segment connecting an object and a reference point. | s-1 | radian per second |
| Angular momentum | L | Measure of the extent and direction and object rotates about a reference point. | kg m2 s-1 | conserved quantity |
| Area | A | The two dimensional extent of an object. | m2 (square metre) | |
| Area density | ρA | The amount of mass per unit area of a two dimensional object. | kg m-2 (kilogram per square meter) | |
| Density (volume density) | ρ | The amount of mass per unit volume of a three dimensional object | kg m-3 (kilogram per cubic metre) | intensive |
| Electric Charge | Q | A s (coulomb) | extensive, conserved quantity | |
| Electric Resistance | R | the degree to which an object opposes the passage of an electric current | m2·kg·s–3·A–2 (ohm) | scalar |
| Energy | E | The capacity of a body or system to do work. | kg m2 s-2 (joule) | extensive, scalar, conserved quantity |
| Force | F | The external cause of acceleration, acting on an object. | kg m s-2 (newton) | vector |
| Frequency | f | The number of times something happens in a period of time. | s-1 (hertz) | |
| Linear density | ρl | Amount of mass per unit length of a one dimensional object. | kg m-1 (kilogram per meter) | |
| Magnetic flux | Φ | Measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. | kg s-2 A-1 (weber) | |
| Momentum | p | Product of an object's mass and velocity. | kg m s-1 (kilogram meter per second) | extensive |
| Power | P | The rate of change in energy over time. | kg m2 s-3 (watt) | |
| Pressure | p | Amount of force per unit area. | kg m-1 s-2 (pascal) | intensive |
| Solid angle | Ω | steradian (sr) | ||
| Speed | v | Rate of change of the position of an object. | m s-1 (metre per second) | scalar |
| Torque (moment of force) | T | Product of a force and the perpendicular disatance of the force from the point about which it is exerted. | kg m2 s-2 (newton metre) | vector |
| Velocity | v | Speed of an object in a chosen direction. | m s-1 | vector |
| Voltage (Electric Potential) | V or ε | Potential difference across a conductor when a current of one ampere dissipates one watt of power. | m2 kg s–3 A–1 | scalar |
| Volume | V | The three dimensional extent of an object. | m3 (cubic metre) | extensive |
| Work | W | Energy dissipated by a force moving over a distance, scalar product of the force and the movement vector. | kg m2 s-2 (joule) | scalar |