Physics -Unit and Dimension

Units are of two type:

Fundamental unit and derived unit

In SI unit there are seven fundamental units:

1. length                       Metre
2. Mass                         Kilogram
3. Time                          Second
4. Current                      Ampere
5. Temperature               kelvin
6. Luminous intensity     Candela
7. Amount of substance  Mole

Beside these 7 units two supplementary units are also defined:

1. radian for plan angle
2. and steradian for solid angle

Some important derived units:

• Force   newton
• Work   joule

Some practical unit of length, mass and time:

• Length  Light year(9.46 * 10^15), Astronomical unit 1.5 * 10 ^11, nautical mile (1852 m), Micron (10^-6), Angstrom (10^-10)
• Mass   Quintal(100 kg), Metric Ton(1000 kg), Atomic mass unit(1.66 * 10^-27 kg), 1 pound(0.45 kg), Chandrasekhar limit (2.8 * 10^30 or 1.4 times the mass of sun)
• Time Solar day(86400 sec), Lunar month(27.3 solar days), Tropical year(total solar eclipse occur) 

Dimension: