Re: Why does the metric system use kg. for unit of weight for humans

   Hello,
   
   The metric system uses kilograms (kg) to denote mass.  On the other hand 
there is the concept of weight which is mass times the acceleration due to 
gravity, which is sometimes denoted in units of Newtons (N).
 
   So, actually the metric system uses kilograms to indicate mass.  The Newton 
indicates a force on a given mass, as in this case, the force directed towards 
the center of the earth if we are looking at the earth's acceleration due to 
gravity to determine the weight of something such as a human. 

   Sometimes people interchange the two because they might sound similiar, but 
in actuality they are two very separate things.  The unit of weight for 
instance is seen less because weight changes for different locations on the 
earth or even for other places outside the confines of our world like the moon 
or other planets.  Mass is an inherent property and should not change for these 
same situations.