Have a question about the fundamentals of the physics engine; How come when you turned the gravity off the ball continued to travel down for some reason? I was expecting the ball to come to a full stop midair as the only force I see effecting the ball IS the gravity. Why does Unity show downward motion of the ball?
When the scene was first played gravity was enabled so the initial drop kept the ball going even with it off. If you turn off gravity the object can still be affected by other physics objects, it just won't fall to the ground like it typically would. Give it a try, add two spheres with rigidbodies. One above the other. Place the one at the top to use gravity and the other to not use gravity.
When the top sphere hits the second ball it'll push it out of the way. Think of these objects as if they were in space, they can still be moved, but they're not affected by gravity. If you don't want them to move at all you can use "Is Kinematic", which tells Unity that you plan on moving this object on your own for something like an animation.
Its also what would happen in real life physics is a falling object suddenly had gravity turned off. Because the ball already has a velocity when you turned gravity off, the ball will stop speeding up towards the ground, but keep moving at the speed it was moving at when you tuned gravity off :)
Hope that makes sense