There is a problem here in that there are actually two definitions of "inertial mass". The first comes from the special relativistic formula Mrel
, where E2
. Frankly, I have never liked this but you see it all the time in elementary textbooks.
The other definition is related to the acceleration of a mass due to a force, such as an electric force or the force of gravity. The main issue is whether two different types of material, such as gold and aluminum weighing the same amount on a scale, have different values of acceleration under a gravitational force. The answer, epitomized by the Eotvos experiment, (see http://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_experiment)
is that there appears to be no difference between two different kinds of material. Hence the term "Equivalence of inertial and gravitational mass".
Yes, general relativity does give corrections to a 1/r2
gravitational force law but it doesn't allow for velocities equal to or greater than c for a particle with a finite rest mass.
(published on 07/21/08)