1. Newton (N = kg m s-2): The newton is the unit of force. One newton is that force which
when applied to a mass of one kilogram produces in it an acceleration of one metre per
2. Joule (J = N m): The joule is the unit of work or energy or quantity of heat. It is also
called newton-metre. It may be defined as the work done when the point of application of
a force of one newton is displaced through a distance of one metre in the direction of the
3. Watt (W = J s-1): The watt is the unit of power or radiant flux. It is equal to one joule
per second or newton metre per second. It may be defined as the power which in one
second gives rise to the energy of one joule.
4. Hertz (Hz=s-1): The hertz is the unit of frequency, It may be defined as the number of
cycles of a regular occurrence completed in one second.
5. Pascal (Pa=N m-2): The pascal is the unit of pressure or stress. It is equal to newton per
metre2.It may be defined as the pressure produced by a force of one newton applied,
uniformly distributed over an area of one square metre.
6. Poise (P =g cm-1): The poise is non- S.I. unit of viscosity, The coherent S.I, unit is
Pa s=kg/m s=N s/m2 which is ten times larger than the poise.
7. Stoke (St = cm 2/s): The stoke is a non- S.I. unit of viscosity, The coherent S.I, unit is
m2/s which is 104 times larger than the stoke.
Derived units of some common physical quantities in M.K.S. and S.I. are: