As for gravitational mass, it is the thing that shows up (twice) in the
expression
Fg = G M m / r2 ([ http://www.av8n.com/physics/mass.htm#eq-grav ]8)
which is valid provided the gravitation is not too strong and not too
rapidly changing.
can you explain this? I'm not sure that I follow what effects you're
alluding to here.
thanks,
Josh Gates
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Physics
Noble and Greenough School
Dedham MA