Airtime is a result of the effects of the
inertia of the train and the riders. As the train goes over a hill transitioning from an ascent into a descent guided by the rails, the inertia of the (albeit loosely) attached riders causes them to momentarily continue upwards, resulting in the riders being lifted out of their seats. The duration of airtime on a particular hill is dependent on the velocity of the train, gravity, and the radius of the track's transition from ascent to descent. Zero-g, where the net vertical g-force is zero, is achieved when the downward acceleration of the train is equal to that of gravity. When the downward acceleration is greater, negative g-forces arise. Airtime is generally understood to fall under two categories: "floater" airtime and "ejector" airtime. Floater airtime provides passengers with the sensation of gently floating upwards, similar to weightlessness. Ejector is more violent and sudden, producing a sharp moment of negative g-forces lifting riders up off their seats before slamming them back down. The
zero-gravity roll is an
inversion specifically designed to create the effect of weightlessness and thereby produce airtime. Flat rides, especially
drop towers, can also provide airtime. == References ==