# How does Zero-G work?

1. Nov 19, 2011

### tahayassen

I understand that the airplane accelerates at the acceleration due to gravity in the downward direction, making the acceleration of the person relative to the airplane zero. But the acceleration due to gravity isn't constant, so I was wondering if someone could show me how you could calculate the acceleration needed for an airplane at certain altitudes?

2. Nov 19, 2011

### tahayassen

Oh, wait. I'm so dumb....

acceleration due to gravity = Gm/r^2

From that formula, you could calculate the acceleration needed at different altitudes. I still don't understand how would I find the equation to model the airplane's position using sine waves. Any ideas?

3. Nov 19, 2011

### D H

Staff Emeritus
Earth gravity decreases by about 0.3086 mGal per meter of increased altitude near the surface of the Earth. This is the free air correction.

As for your question, this is very tiny, even for a couple of kilometers of altitude change.

4. Nov 19, 2011

### rcgldr

During the zero g portion of flight, the airplane is following a parabolic path (technically an elliptical path if you don't consider the earth to be flat), with a downwards acceleration of 1 g and near constant horizontal component of velocity.