Uhm, actually, if you want forces to be generated via acceleration, you need relativistic accelerations. So, Earth would have to accelerate, and we would have to not be. So, if you throw a rock up into the air, your hypothesis states that the rock either loses the acceleration it had, or that it never had it, that the earth would have to have a propulsion system completely underneith it. Meaning that there is matter being ejected off the bottom of the earth, with increasing speed, since the law of conservation of momentum states that in order to increase something's momentum one way, another object has to push off it the other way. This matter would of course need a supply of itself, and an energy supply that could increase in potentency constantly. And, actually, relativisticly to the ejected matter from this propulsion system, since it's going backwards, we would be going at increasingly closer to light speed, meaning that this matter would increase in mass even more, due to the formula for mass expansion, which I think is M = Mo/(1-(v^2/c^2), so... umm, it's increasing to a double square function. It would also mean, that this incredibly strong force pushing on the bottom of the earth would have to *not* break it apart, somehow. The mass being ejected from the bottom of the earth also has to be gravity-less, since eventually the mass from the fuel would start hitting us with a ginormous gravity field if it emitted one, since its mass is being increased relativistically, I think, I'm no whiz at relativity.
haha, sorry dude, I tried.