Units and Fundamental Constants
Units are in the International System (SI), now the accepted standard.
Quantity Unit Symbol Notes
Fundamental Units
Mass kilogram kg
Length meter m
Time second s
Angle radian rad There are 2p radians in a circle
Temperature Kelvin K T(K)=T(C)+273.16
Number mole mol 6.022 x 1023 molecules
Derived Units
Linear Velocity m s-1
Acceleration m s-2
Angular Velocity rad s-1
Energy Joule J (= kg m2 s-2)
Force Newton N (= kg m s-2)
Pressure Pascal Pa (= N m-2 = kg m-1 s-2)
Power Watts W (= J s-1 = kg m2 s-3)
Viscosity Pa s (= kg m-1 s-1)
Frequency Hertz Hz (=s-1)
Some Non-SI Units
Length ngstrom 1 = 1x10-10 m
Energy electron volt eV 1 eV=1.60219 x 10-19 J
Energy calorie cal 1 cal = 4.184 J
Pressure bar bar 1 bar = 105 Pa
Prefixes
k M G T c m m n p f
kilo- mega- giga- tera- centi- milli- micro- nano- pico- femto-
103 106 109 1012 10-2 10-3 10-6 10-9 10-12 10-15
Some Fundamental Constants
Avagadro's Number NA 6.022 x 1023
Boltzmann Constant k 1.3806 x 10-23 J molecule-1 K-1
Gas Constant R=kNA 8.3143 J mol-1 K-1
Speed of Light in vacuum c 2.998 x 108 m s-1
Planck Constant h 6.626 x 10-34 J s
Atomic Mass Unit amu 1.661 x 10-27 kg
Mass of electron me 9.10939 x 10-31 kg
Square of electron charge e2 2.30707 x 10-28 J m 14.40 eV