Kind of I guess. Gravity affects objects which have a mass and gravity cant be turned on or off. Also in the world we live theres friction between pretty much everything you do that moves or collides. This means that a perpetual motion machine using gravity isn't possible because 1) an object fall, great this could be used to power a turbine with the falliing motion, but how does it get back up? 2) If an object were to bounce, it would never reach its point of origin due to wind resistance (my bit above) Unless there was a force at the point where it impacts the ground which propells it back up Maybe a big ball could fall, power a turbine and get propelled back up by a spring? Dunno lol