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Originally Posted by DonQuigleone
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@Jinto, All forces accelerate masses, that's what a force is. And you need force to overcome inertia. But the inertia isn't being "nullified", it's just being err "counteracted". It never becomes a non-factor.
Also your mechanics are a bit faulty there. To produce acceleration, you must have a force of some kind. That is how acceleration of a mass occurs. IE Force = Mass X Acceleration. You cannot have an "unknown" acceleration. In your case the gravitational force is counteracting the accelerating force, in which case the body in question will not feel any acceleration at all.
Inertia is not precisely a force to be counteracted, it is simply the property of a body to resist acceleration. This is not an additive factor, but a multiplicative factor. Mathematically, depending on the scenario, the inertia of a body is identical to it's mass, or alternatively it's momentum.
The resistance that you might thinking of overcoming is friction or air resistance, which in itself is a set of forces. In a vacuum like outer space, these do not occur. On earth, this leads to the often mistaken idea that you need constant force to propel a body forwards. This is false, you only need constant force to overcome friction, and then further force to produce acceleration (not velocity).
This is why I say you cannot "nullify" inertia. Inertia is why the same force accelerates a small bullet forward at hundreds of meters a second, but only causes the person holding the gun to be pushed back a little bit. The person, possessing larger mass, has more inertia then the tiny bullet. The same force produces a far more dramatic effect on the bullet.
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I acknowledge that we are just arguing over semantics here. I suppose you understood what I tried to say. Btw. only forces that actually interact with masses can accelerate masses. Hence my distinction. Take the gravitational force that is only supposed to interact with the mass of traveller in the spaceship but not the spaceship itself (I know its hypothetical, but its important to make the whole thing work).
Of course I am aware that you cannot truely nullify inertia, only the resulting forces (for me thats just semantics though).