Thank you so much, TurtleMeister, for the warm welcome and reply to my question. When I tried to find information about initial mass and gravitational mass I found this thread and when I read Cavendish's experiment I found that to calculate the Earth's mass and density (then people used his...
Can someone tell me why in Cavendish's experiment he used the inertial masses to measure the graviational constant?
http://en.wikipedia.org/wiki/Cavendish_experiment