A physical quantity is a property of a material or system that can be quantified by measurement. In physics, a physical quantity is any physical property of a material or system that can be quantified, that is, can be measured using numbers.A physical quantity can be expressed as a value, which is the algebraic multiplication of a numerical value and a unit. Examples of physical quantities include: Mass, time, length, current, density, etc.
Physical quantities are generally classified into two. These are:
Scalers are physical quantities that have numerical values only. They possess magnitude only.They do not give us information about direction. For instance, a man walks a distance of 3m. This statement only gives us the measurement or the length the man covered but doesn't tell us where(direction) the man went to. Examples of scalers include: mass, work, distance, current, distance, speed, energy, etc.
Vectors are physical quantities that possess
both magnitude and direction. They give us information about the
direction of the quantity. Examples are displacement, force, acceleration, velocity, weight, gravity, pressure,
etc
Unit can be defined as the quantity of a constant magnitude which is used to measure the magnitudes of other
quantities of the same nature. Physical quantities are measured using units. The universally accepted system of
units
is the International System of Units (SI). Examples of SI units include: metre(m), seconds(s),
kilogram(Kg), etc
Physical quantities are often times divided into fundamental and derived quantities.
Fundamental quantities are quantities that are independent of other quantities. They are called basic quantities because other quantities are derived from them. The units of measuring fundamental quantities are called fundamental units
| Physical Quantity | Symbol | Unit |
|---|---|---|
| Length | L | meter (m) |
| Mass | m | kilogram (kg) |
| Time | t | second (s) |
| Electric Current | I | ampere (A) |
| Temperature | T | kelvin (K) |
| Amount of Substance | n | mol (mole) |
| Luminous Intensity | Iv | candela (cd) |
Derived quantities are quantities which are gotten by the combination of one or more fundamental quantities. Derived quantities are gotten by algebraic operations on fundamental questions. The units of measuring derived quantities are called derived units
| Derived Quantity | Unit | Symbol |
|---|---|---|
| Velocity | m/s | v |
| Acceleration | m/s² | a |
| Force | Newton (N) | F |
| Pressure | Pascal (Pa) | P |
| Energy | Joule (J) | E |
| Power | Watt (W) | P |
| Electric Current | Ampere (A) | I |
| Voltage | Volt (V) | V |
| Resistance | Ohm (Ω) | R |
| Frequency | Hertz (Hz) | f |
| Angular Velocity | Radian per second (rad/s) | ω |
| Displacement | Meter (m) | Δx |
| Momentum | Kilogram meter per second (kg m/s) | p |
| Torque | Newton meter (N m) | τ |
| Electric Charge | Coulomb (C) | Q |
| Electric Potential | Volt (V) | V |
| Electric Resistance | Ohm (Ω) | R |
| Acceleration due to Gravity | Meter per second squared (m/s²) | g |
| Electric Capacitance | Farad (F) | C |
| Angular Acceleration | Radian per second squared (rad/s²) | α |