I'm trying to learn what is the difference between the inertial and gravitational mass. According to: http://www.physlink.com/education/askexperts/ae305.cfm and https://www.physicsforums.com/showthread.php?t=147282 there is practically no difference (as stated by the Equivalence principle) other than the method to find it out. Does that mean for example that when on the Moon the gravity is six times weaker than on the Earth I can with the same force accelerate an object to six times the speed as on the Earth? And then when in a freefall orbit where there is no gravity I can accelerate arbitrary massive object to any speed because it doesn't have any gravitational and thus inertial mass (following the Equivalence principle)? That doesn't make sense, does it? Then how can be the gravitational and inertial mass the same?