(I) Astronomical Unit
It is the mean distance of the earth from the sun.
1 AU = 1.496×10¹¹ m
(II) Light Year
It is the distance travelled by light in vacuum in 1 year.
1 ly = 9.46×10¹⁵ m
(III) Parallactic Second
It is the distance at which an arc of length 1 astronomical unit subtends an angle of 1 second of arc.
1 Par Sec = 3.084×10¹⁶ m = 3.26 ly
(IV) Micron or Micrometre
1 μm = 10⁻⁶ m
1 nm = 10⁻⁹ m
(VI) Angstrom Unit
1 A⁰ = 10⁻¹⁰ m
This unit is used for measuring nuclear size.
1 Fm = 10⁻¹⁵ m
(I) Pound, 1 Pound = 0.4536 kg
(II) Slug, 1 Slug = 14.59 kg
(III) Quintal, 1 Q = 100 kg
(IV) Tonne, 1 Ton = 1000 kg
(V) Atomic Mass Unit :- it is defined as the 1/12 th of the mass of one ₆C¹² atom.
1 amu = 1.66×10⁻²⁷ kg
(I) Solar Day:- It is the time taken by the earth to complete one rotation about its own axis with respect to Sun.
(II) Solar Year:- It is the time taken by the earth to complete one revolution around the sun in its orbit.
1 Solar Year = 365.25 Days = 366.25 sedrial days