A soccer ball painted safety orange, a stop-watch, an isolated corn field, and a -1 G gravity warp.  A long minute later the ball hit the ground at about 180 mph.  Jennifer renewed her Hippocratic oath and snuck very quickly out of the corn field.

Note on Game Mechanics:  The duration of gravity control got some discussion on the WebRPG forum, but David hasn't yet issued a ruling for the Four Winds game.  The debate hinged on the problem that the warp creator cannot maintain a warp that is out of range.  Gravity's range is 18 game inches (90 feet).

If the warp lasted a full one turn (15 seconds) the ball would land approximately 50 seconds later travelling at terminal velocity (about 180 mph for a smooth spherical object, which I think will destroy a soccer ball).  This duration is implied in the rules because the warp creator can spend one action per turn to maintain any warps in range; suggesting a one turn base duration.

However, if the warp ends immediately once out of range, it means that the soccer ball above would leave Gravity's range in just under 2.4 seconds.  An eight second round trip would impart veleocity of 72mph (well within design parameters for a soccer ball, if I recall correctly).