## Physics - Fundamental Units and Derived Units

*①*In mechanics, there are three physical quantities namely mass length and time which are called fundamental physical quantities.

*②*These units are called fundamental because they are all independent of each other.

*③*Discussing other branches of Physics, we find other physical quantities like temperature luminous intensity electric current and the amount of substance are also called fundamental physical quantities. For example Calvin (K), candela (Cd) Ampere (A) and mole(mol) respectively are called fundamental units.

*④*In addition Radian for plane angle and steradian for solid angle are two supplementary fundamental units.

*⑤*Fundamental units are independent of each other. The units which are not independent of each other and are dependent from fundamental units are called derived units. Examples of derived units are area, velocity, acceleration, volume, force etc.

*⑥*International System of Units (SI units) identify the following as seven fundamental units

⑴ metre (m - for length)

⑵ kilogram (kg for mass)

⑶ second (for time)

⑷ kelvin (for temeprature)

⑸ candela (for luminous intensity)

⑹ mole (for amount of substance)

⑺ ampere (for current)

Two supplementary units are:

⑻ radian (for plane angle)

⑼ steradian (for solid angle)

__Exercise__

**Directions**: Write down the SI unit and its symbol for the following physical quantities:

Distance :

Mass :

Time :

Current :

Temperature :

Luminous Intensity :

Angle :

Solid Angle :

Force :

Energy :

Speed :

Angular Velocity :

Frequency :

Moment Of Inertia :

Momentum :

Angular Momentum :

Pressure :

Power :

Surface Tension :

Viscosity :

Electric Charge :

Potential :

Capacitance :

Electrical Resistance :

Inductance :

Luminous Flux :

Optical Wavelength :

Impulse :

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