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